Equipment
Ingredients
Shortbread Crust
- 125 g all-purpose flour
- 50 g granulated sugar
- 115 g unsalted butter, melted and slightly cooled
- 1 g fine sea salt
Lemon Filling
- 200 g granulated sugar
- 25 g all-purpose flour
- 4 eggs, room temperature
- 120 ml freshly squeezed lemon juice
- 10 g lemon zest
Garnish
- 15 g powdered sugar
Nutrition (per serving)
Nutrition is estimated per serving. Nutrients without complete source data are omitted.
Full nutrition
- Calories
- 170 kcal
- Protein
- 3 g
- Carbohydrates
- 24 g
- Fat
- 7 g
- Fiber
- 0 g
- Sugar
- 17 g
- Sodium
- 43 mg
- Saturated Fat
- 4 g
- Trans Fat
- 0 g
- Monounsaturated Fat
- 2 g
- Polyunsaturated Fat
- 1 g
- Cholesterol
- 62 mg
- Potassium
- 38 mg
- Calcium
- 12 mg
- Iron
- 0.3 mg
- Magnesium
- 4 mg
- Phosphorus
- 37 mg
- Zinc
- 0.2 mg
- Vitamin A
- 69 mcg
- Vitamin C
- 4 mg
- Vitamin D
- 0.3 mcg
- Vitamin E
- 0.3 mg
- Vitamin K
- 1 mcg
- Vitamin B6
- 0.0 mg
- Vitamin B12
- 0.1 mcg
- Thiamin
- 0.02 mg
- Riboflavin
- 0.07 mg
- Niacin
- 0.1 mg
- Folate
- 10 mcg
- Water
- 19 g
Sources: USDA FoodData Central
Method
Preheat the oven to 175°C (350°F). Line a 20x20cm baking pan with parchment paper, leaving enough overhang on the sides to easily lift the bars out later.
In a mixing bowl, combine the all-purpose flour, granulated sugar, melted unsalted butter, and fine sea salt for the crust. Mix until a thick, crumbly dough forms.
Press the dough evenly into the bottom of the prepared baking pan. Bake for 18 to 20 minutes until the edges are lightly golden brown.
While the crust is baking, prepare the filling. In a separate mixing bowl, whisk together the granulated sugar and all-purpose flour. Add the eggs, freshly squeezed lemon juice, and lemon zest. Whisk gently just until smooth and combined.
Carefully pour the liquid lemon filling directly over the hot, freshly baked crust.
Return the pan to the oven and bake for another 20 to 25 minutes. The bars are done when the center is set, no longer jiggles, and reaches an internal temperature of 74°C (165°F).
Remove from the oven and allow to cool completely in the pan at room temperature for at least 2 hours. This step is crucial for the filling to set fully.
Once completely cooled, use the parchment overhang to lift the slab out of the pan. Using a chef knife, slice into 16 uniform squares. Use a fine mesh sieve to dust the tops generously with powdered sugar just before serving.
Chef's Notes
- Pouring the liquid filling over a hot crust is essential. The heat begins cooking the custard immediately, creating a seal that prevents the liquid from seeping under the shortbread.
- Always use freshly squeezed lemon juice. Bottled lemon juice contains preservatives and oils that significantly mute the bright, tart flavor essential to this classic dish.
- For the cleanest, most professional slices, use a sharp, warm chef knife and wipe the blade completely clean with a damp towel between every single cut.
- When zesting the lemons, be careful to only remove the bright yellow outer skin. The white pith underneath is extremely bitter and will impart an unpleasant taste to your dessert.
Storage
Refrigerator: 1 week — Store in an airtight container. Dust with fresh powdered sugar before serving as the original sugar will absorb into the moisture of the filling.
Freezer: 3 months — Freeze fully cooled squares without powdered sugar, separated by parchment paper.
Troubleshooting
White, foamy sponge layer on top of the baked bars
Cause: Eggs were whisked too vigorously, incorporating excess air into the filling
Fix: Cosmetic issue only. Dust heavily with powdered sugar to conceal the foam layer
Prevention: Whisk the filling gently just until the eggs are broken up and the ingredients are combined
Filling is runny and seeps out when cut
Cause: Bars were underbaked or sliced while still warm
Fix: Chill in the refrigerator for 2 to 3 hours to help the residual butter and eggs firm up
Prevention: Bake until the center no longer wobbles and allow a full 2 hours to cool
Crust is soggy and filling seeped underneath
Cause: Filling was poured onto a cooled crust
Fix: Cannot be fixed
Prevention: Always pour the filling over the crust while the crust is still piping hot from the oven
Cultural Context
Lemon squares, often called lemon bars, became an American baking staple in the mid-twentieth century. The first widely printed recipe appeared in the Chicago Daily Tribune in August 1962. They perfectly encapsulate the tradition of potluck and bake-sale desserts, offering a bright, sunshine-like contrast to heavy chocolate confections, making them especially popular for Easter and springtime gatherings.
