1 cup unsalted butter, softened
2 cups all-purpose flour
1/2 cup powdered sugar
1 1/2 cups granulated sugar
1/4 cup all-purpose flour
4 large eggs
1/2 cup freshly squeezed lemon juice
1 tablespoon lemon zest
1/4 teaspoon salt
4 large egg whites
1/2 cup granulated sugar