1. |
Heat oven to 350 °F (175 °C). Spray 8" x 8" baking pan with cooking spray. |
2. |
Mix 1 cup of the flour, 1/4 cup of sugar, and salt in bowl until well combined. Cut the butter into flour mixture until a crumbly dough forms. |
3. |
Press dough evenly into bottom of prepared baking pan. Bake until lightly golden (about 10-12 minutes). Cool crust completely. |
4. |
Whisk egg, egg white, and remaining 1/2 cup of sugar in bowl until combined. Grate zest and squeeze juice from lemon and add to egg mixture. Add baking powder and remaining 3 tablespoons of flour. Mix thoroughly. |
5. |
Pour liquid mixture over cooled crust. |
6. |
Bake until set and lightly browned on edges. This will take approximately 20 to 25 minutes. |
7. |
Cool completely and dust top with powdered sugar and cut into 16 squares. |