Lemon Rhubarb Bars
Refreshingly tart rhubarb enveloped in a sweet lemony custard layer with a buttery shortbread base. Topped with toasted Swiss meringue, these bars are an excellent way to highlight the vibrant pink color and unique flavor of rhubarb as it makes its all-too-brief appearance in spring.
Servings 16 bars (8 inch square pan)
Ingredients
SHORTBREAD CRUST
- 113 grams unsalted butter chilled, cubed
- 50 grams granulated sugar
- 120 grams all purpose flour
- ¼ teaspoon kosher salt Diamond Crystal
LEMON RHUBARB CUSTARD LAYER
- 23 grams all purpose flour
- 150 grams (¾ cup) granulated sugar
- 2 large eggs beaten
- 60 mL heavy cream
- lemon zest from 1 large lemon
- 60 mL lemon juice freshly squeezed, from the same lemon
- 2.5 mL lemon oil
- 366 grams rhubarb diced
SWISS MERINGUE TOPPING
- 100 grams egg whites ~3 large egg whites
- 150 grams granulated sugar
- 1.25 mL 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 unsalted butter, 50 grams granulated sugar, 120 grams 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 large mixing bowl, whisk together flour and sugar.23 grams all purpose flour, 150 grams (¾ cup) granulated sugar
- Add eggs and whisk to combine.2 large eggs
- Add heavy cream. Zest the lemon directly into the cream. Add lemon juice and lemon oil and whisk until completely blended.60 mL heavy cream, lemon zest, 60 mL lemon juice, 2.5 mL 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 rhubarb
- Bake at 350° F (177C, gas mark 4) for 40-45 minutes, until custard layer is completely set - it should not jiggle. Place on a metal rack to cool. 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 granulated sugar, 1.25 mL 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: 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: 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.