Tart Lemon-Cheese Cake

Beat butter at medium speed with an electric mixer until creamy; gradually add sugar, beating well.

Combine water and milk in a small bowl; set aside.

Combine flour, baking powder, and salt; add to butter mixture alternately with milk mixture, beginning and ending with flour mixture.

Mix at low speed after each addition until blended.

Stir in rum flavoring.

Beat egg whites at high speed until stiff peaks form; gently fold into batter.

Pour batter into three greased and floured 9 inch round cake pans.

Bake at 350 degrees for 20 to 25 minutes or until a wooden pick inserted in center comes out clean.

Cool in pans completely.

Spread lemon-cheese filling between layers and on top of cake.

Spread lemony white frosting on sides.

Garnish with lemon slices, if desired.