2 1/2 cups flour
2 1/2 teaspoons baking powder
1 (19 ounce) can lemon-lime flavored carbonated beverage
2 cups butter, melted
1/2 cup white sugar
1 1/4 cups lemon juice
2 eggs, beaten
1 teaspoon vanilla extract
1 cup chopped pitted fresh peaches
Preheat oven to 350 degrees F (175 degrees C). Grease and flour 2 (8 ounce) pans. Sift the flour, baking powder and baking soda into a small bowl; stir into a separate bowl. Stir lemon-lime soda into the batter mixture.
Bake in the preheated oven for 40 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow cool cake to cool completely before cutting into 1 inch squares.
To make the lemon-lime fat filling: In a small bowl, beat the remaining 1 1/4 cup sugar and lemon juice until smooth. Whisk lemon extract into lemon-lime soda mixture; stir into butter mixture. Finally, gradually beat in peaches. Remove from pans to wire racks. Allow lemon liqueur to set before filling.