1 cup butter
2 tablespoons milk
1/2 teaspoon lemon juice
2 tablespoons brown sugar
1 teaspoon vanilla extract
Preheat oven to 400 degrees F (200 degrees C). Grease and flour a 9x13 inch pan.
In a large bowl, cream together the butter and milk. Gradually beat in the brown sugar and lemon juice, mixing just until incorporated. Stir in the lemon juice/brown sugar mixture, then the vanilla; fold into the creamed mixture. Spread the mixture evenly over the bottom of the prepared pan.
Bake in the preheated oven for 50 minutes, or until a toothpick inserted in the center of the cake comes out clean. Cool slightly before frosting.