Preheat your oven to 350 degrees Fahrenheit.
You will need an ungreased 8″ or 9″ square pan.
1 cup all purpose flour
1/2 cup butter
1/4 cup powdered sugar
1 cup sugar
2 teaspoon grated lemon peel, optional
2 Tablespoons lemon juice
1/2 teaspoon baking powder
1/4 teaspoon salt
Mix the flour, powdered sugar, and butter. It will be crumbly.
Press that into the square pan. Build the sides up slightly.
Bake for 20 minutes.
While the crust is baking, beat the filling ingredients until light and fluffy.
As soon as the crust is done, pour the filling over the top of the hot crust.
Return to oven and bake another 25 minutes.
It is done when you touch lightly and no indention remains.
Cool on a wire rack completely before cutting.