These lemon rhubarb bars feature a sweet and tart lemon custard that envelops a generous amount of vibrantly hued rhubarb. With a buttery shortbread base and a decorative toasted meringue topping, they're are an excellent way to celebrate the arrival of rhubarb in gardens and local shops.
I've been eagerly awaiting the arrival of rhubarb to my local grocery stores. Just as citrus fruits signal the shift of seasons into winter, rhubarb is firmly stuck in my mind as one of the first signs that spring is truly on its way.
Around the same time that the flowering fruit trees burst into colorful cotton candy blooms, those first brightly pink and red hued stalks appear. The growing season for rhubarb is brief, so I try to take advantage whenever I see it. I've used it in cakes, tarts and pies - including this rhubarb frangipane tart and a strawberry lime rhubarb slab pie.
Here I wanted to incorporate the rhubarb into a recipe for shortbread bars, and took inspiration from an old fashioned dessert favorite, rhubarb custard dessert bars, but with a lemony custard filling and no mysterious "whipped toppings."
Not quite a lemon bar, nor a rhubarb custard bar, I've married the two by adding three types of lemon (freshly squeezed lemon juice, lemon zest and lemon oil) and a generous amount of diced rhubarb.
The origin matters less than the end result: a vibrant, brightly flavored bar packed with a balance of sweet custard, rich shortbread crust, and the inevitable zing from tart lemon and rhubarb combined. It's all tempered with a sweet decorative layer of toasted Swiss meringue that ties it all together nicely.
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Ingredients
* See recipe card for detailed list of ingredients and quantities.
Unsalted butter - Using unsalted butter allows you to control the total amount of salt in the recipe.
Lemon oil - I use lemon oil in this recipe to add an extra boost of lemon flavor to the custard filling. Lemon oil is concentrated and really helps achieve a powerful tang. I find it to be much more flavorful than lemon extract.
Swiss meringue
Making a Swiss meringue requires a bit more effort than common meringue, but it has a stronger structure, which helps keep the meringue stable over a longer period of time.
Although these bars are really best soon after making them, I stored extra meringue topped bars in the fridge for several days and they held up just fine with no weeping. You can either spread a full layer of meringue onto the top, pipe meringue decorations on each bar.
If you spread meringue to cover the entire top, you'll cover the vibrant red and pink hues of the rhubarb, but you'll gain the sweet taste of meringue with every bite of lemon rhubarb bar. The next time I make them, I'm considering more meringue as it's such a delicious pairing.
Equipment
8 inch square pan - I use an 8 inch square metal pan by USA Pans for this recipe - and for most of my bar cookies.
16 inch piping bag - A large piping bag is great for adding decorative details with the Swiss meringue.
Piping tip - A St. Honore tip would be ideal for the zig zag pattern that I piped. I didn't have one and ended up using an Ateco 366 leaf tip.
Be creative with the piping - most large or jumbo tips with a wide enough opening will work well for meringue.
If you choose to pipe decorative meringue patterns rather than covering the whole top, you'll likely end up with some leftover meringue.
To avoid food waste, consider making piped meringue kisses. Pipe onto parchment and cook in a 200 degree F (93 degrees C) oven for 2 to 2 ½ hours.
Frequently asked questions
For best results, eat these bars fresh and store any extra in the fridge for up to 5 days in a single layer airtight container.
Most dessert recipes that have a custard element aren't frozen after baking. They tend to separate and turn watery.
Rinse the stalks in water to remove any dirt. Remove any remaining leafy green portion. Rhubarb leaves can be toxic in large amounts as they contain high amounts of oxalic acid (though you'd have to consume a significant amount to feel the ill effects).
If the stalks are thicker than your thumb in width, split them lengthwise. I found early forced rhubarb which tends to be smaller in diameter, so I didn't need to split mine (read more about forced rhubarb vs. regular rhubarb). Dice stalks into even pieces about the size of your thumbnail.
Love this recipe? Please leave a comment and star rating. ★★★★★ Your feedback, suggestions, and adaptations are very helpful to other bakers!
📖 Recipe
Lemon Rhubarb Bars
INGREDIENTS
SHORTBREAD CRUST
- 113 grams (½ cup, 4oz) unsalted butter, chilled, cubed
- 50 grams (¼ cup) granulated sugar
- 120 grams (1 cup) all purpose flour
- ¼ teaspoon kosher salt, (I use Diamond Crystal)
LEMON RHUBARB CUSTARD LAYER
- 23 grams (3 Tbsp) all purpose flour
- 150 grams (¾ cup) granulated sugar
- 2 large eggs, beaten
- 62 mL (¼ cup) heavy whipping cream
- 62 mL (¼ cup) lemon juice, freshly squeezed (approximately 1 large lemon)
- lemon zest, from one lemon
- ½ teaspoon lemon oil , or extract
- 366 grams (3 cups, 0.8lb) rhubarb, diced
SWISS MERINGUE TOPPING
- 100 grams egg whites, approximately 3 large egg whites
- 150 grams (¾ cup) granulated sugar
- ¼ teaspoon vanilla extract
INSTRUCTIONS
SHORTBREAD LAYER
- Preheat the oven to 350° F (177 C, gas mark 4).
- Line an 8" (20 cm) square pan with parchment paper, extending a flap of parchment over opposite sides as a handle to aid in removing the bars later.
- In the bowl of a stand mixer fitted with the paddle attachment, combine the butter, sugar, flour, and salt and mix until the dough begins to come together with a lumpy, sandy texture.113 grams (½ cup, 4oz) unsalted butter, 50 grams (¼ cup) granulated sugar, 120 grams (1 cup) all purpose flour, ¼ teaspoon kosher salt
- Dump the dough into the prepared pan and press with your fingers until it is spread evenly into all areas of the pan. Cover with plastic wrap and use the flat base of a drinking glass or the bottom of a measuring cup to smooth the top and firmly pack down the dough. Chill in the fridge for 30 minutes.
- Bake the shortbread for 10-12 minutes, until top has gone from shiny to dull, shortbread is just baked through, barely starting to turn golden brown, and beginning to smell like toasted butter. Remove from oven and set aside to cool on a baking rack.
LEMON RHUBARB CUSTARD LAYER
- In a medium size bowl, whisk together flour and sugar.23 grams (3 Tbsp) all purpose flour, 150 grams (¾ cup) granulated sugar
- Add eggs and whisk to combine.2 large eggs
- Add cream, lemon juice, lemon zest and lemon oil and mix until completely blended.62 mL (¼ cup) heavy whipping cream, lemon zest, 62 mL (¼ cup) lemon juice, ½ teaspoon lemon oil
- With a spatula, fold in diced rhubarb and pour mixture onto cooled shortbread crust. Rap pan firmly on countertop several times to remove air bubbles that may have formed in custard.366 grams (3 cups, 0.8lb) rhubarb
- Bake at 350° F (177C, gas mark 4) for 40-45 minutes, until custard layer is completely set - it should not jiggle. Cool completely on a rack. Once cool, place in refrigerator to set for at least one hour.
SWISS MERINGUE TOPPING
- In a small (1 qt ) saucepan, whisk together egg whites, sugar and vanilla extract. Warm over low heat, whisking frequently, until mixture is warm and granulated sugar has dissolved.100 grams egg whites, 150 grams (¾ cup) granulated sugar, ¼ teaspoon vanilla extract
- Rub some of the egg white mixture between your fingers (carefully - it might be hot). If you feel sugar granules, keep mixing until it feels smooth. If you have a thermometer, it should read 160° F (177 C).
- Transfer warm egg mixture to the bowl of a stand mixer fitted with the whisk attachment. Beat until stiff peaks forms and mixture has a glossy sheen - about 5 minutes. The meringue should be very thick and hold its shape (no drooping) when the whisk is dipped into the mixture and turned upright.
- Remove fully chilled bars from pan. Place bars onto a metal baking sheet, removing the parchment paper from underneath.Kitchen torches and paper do not mix!
- Option 1 - Spread meringue over bars: Scoop the meringue out onto the fully cooled bars. Spread evenly to cover the filling, making swirls with an offset spatula or spoon. Toast the meringue using a torch. Slice into 16 squares, wiping the knife clean in between each cut.
- Option 2 - Pipe meringue onto bars: Slice into 16 squares, wiping the knife clean in between each cut. Pipe the meringue onto individual bars using a 16" (40cm) piping bag fitted with a decorative tip. Toast the meringue using a torch.
- Serve promptly. Keep additional bars refrigerated in a single layer in an airtight container.
EQUIPMENT
- 8 inch square baking pan
Helen says
Made this for a lunch and it was so beautiful. Lovely the lemon/tang/sweet combination. I wouldn't change a thing.
Nancy says
Amazing!
First rhubarb picking of the year and happy I chose this recipe!
Kathleen Culver says
Thanks so much, Nancy!
I'm on the lookout for rhubarb this spring. Sounds like you have a patch of your own.
Lucky you!
Kathleen
Ellie says
I made this. It was beautiful and tasted perfect! Very accurate and straightforward recipe that was easy to follow. Very delightful dessert!
Kathleen Culver says
I'm so happy to hear that, Ellie.
Thanks so much for the review and your comments - I appreciate them very much!!
Kathleen
Yvonne says
These bars are the perfect marriage of lemon and rhubarb .
Flavors of Spring❤️
Kathleen Culver says
So glad you like them, Yvonne!
Thanks so much.
Kathleen
Kathy Milne says
The flavour of lemon and rhubarb and the shortcrust pastry was sublime! But
for those who don't have the needed over 2 1/2 hrs from start to finish( 2 fridge cooling times of 30 min and 1 hr in addition to prep and bake times) here are a couple of short cuts that work well
I did my pastry in the food processor and didn't chill it before I baked, cooled for about 10 min and then topped with the rhubarb filling. Once baked i cooled on a rack and it sliced well with a sharp knive, not refrigerated. I prefer the bars slightly warm or room temp for better flavour. Cold just didn't taste as good.
And as my time was more limited instead of topping with meringue I topped with whipped cream.
These are well worth making and to share again!
Kathleen Culver says
Thanks so much for the great feedback, Kathy!
I'm glad you enjoyed them.
Kathleen
Kimberly says
Hi there! I'm at work surfing around your blog from
my new iphone! Just wanted to say I love reading through
your blog and look forward to all your posts! Carry on the outstanding work!
Kathleen Culver says
Thanks so much for visiting, Kimberly!
Kathleen
Terri Soulen says
I made these today for dinner guests. They were GORGEOUS and absolutely delicious-the perfect balance of tart and sweet. I took your advice and used lots of meringue. My St Honore tip piping needs work, but they were fabulous nevertheless. Now I have another reason to look forward to rhubarb season. Thanks for the great recipe.
The Floured Table says
Hi Terri,
Thank you so much for the sweet comment. I'm so thrilled to know that you and your guests enjoyed them.
I need to get myself a St. Honore tip ASAP - I'm sure I'll need practice too!
With appreciation,
Kathleen