For the crust:
- 1 cup (2 sticks) unsalted butter
- 1/2 cup granulated sugar
- 2 cups Bob’s Red Mill Gluten Free 1-to-1 Baking Flour
- Pinch salt
For the filling:
- 6 jumbo/extra-large eggs, room temperature
- 3 cups granulated sugar
- 2 tablespoons lemon zest (from about 4–6 lemons)
- 1 cup fresh lemon juice
- 1 cup Bob’s Red Mill Gluten Free 1-to-1 Baking Flour
- Powdered sugar, for topping
- Heat oven to 350F. Line a 13×9-inch baking pan with foil, with enough overhang on opposite ends to use as handles.
- In a small saucepan over medium heat, melt butter. Once butter is melted, continue to cook over medium heat, stirring constantly, until butter gets creamy, then foamy and clear and finally begins to turn a golden brown color. Immediately remove from heat; pour into a small heatproof bowl. Refrigerate until butter just returns to its solid form but remains soft, about 1 hour.
- In a large bowl using an electric hand mixer, or in the bowl of a stand mixer with the paddle attachment, cream solid butter and 1/2 cup sugar on medium speed until light and fluffy, about 2-3 minutes. Stir in 2 cups flour and salt just until a dough forms. Using lightly floured hands or a spatula, gently press dough evenly into bottom of prepared baking pan. Chill 15 minutes.
- Bake dough 17-23 minutes or until just set in center and lightly golden. Set on a cooling rack to cool slightly while you make the filling.
- In a large bowl, whisk eggs until beaten. Slowly beat in 3 cups sugar, lemon zest and lemon juice until well combined. Slowly beat in 1 cup flour until mixture is smooth and no lumps remain.
- Pour filling on top of hot crust. Bake 30-35 minutes until filling is just set. Cool completely on a cooling rack, about 2 hours.
- Use foil as handles to carefully remove bars from baking pan. Use a very sharp, clean knife to cut into 24 squares. Dust generously with powdered sugar. Store covered in the refrigerator for up to 3-4 days.