Preheat oven to 350°F. Prepare cake mix as directed on package. Remove 1 1/2 cups of the batter to medium bowl. Stir in 1 tablespoon of the raspberry flavor and red food color. Pour into greased 8-inch square baking pan. Reserve remaining batter.
Bake 12 minutes or until toothpick inserted into center comes out clean. Cool on wire rack. Cut out heart shapes with 2-inch heart-shaped cookie cutter. Set aside.
Stir vanilla into reserved batter. Pour 1/2 of the batter into 8-inch loaf pan sprayed with no stick cooking spray. Press cake hearts vertically into cake batter along center of loaf pan. Pour remaining batter over top. Bake 40 to 45 minutes or until toothpick inserted into center of white cake comes out clean. Cool cake in pan 10 minutes. Remove from pan; cool completely on wire rack.
Meanwhile, beat butter and remaining 2 teaspoons raspberry flavor in large bowl until light and fluffy. Gradually add confectioners' sugar alternately with cream, beating well after each addition and scraping sides and bottom of bowl frequently. Frost cooled cake with frosting.