Cream butter in a large mixing bowl; add brown sugar, and beat until light and fluffy. Gradually add flour, mixing well. Press mixture evenly into an ungreased 13- x 9- x 2-inch baking pan. Bake at 350° for 25 minutes; remove from oven, and set aside.
Combine sour cream, 1 tablespoon plus 1 1/2 teaspoons sugar, and vanilla; beat at medium speed of an electric mixer until well blended. Spread evenly over baked mixture. Bake an additional 10 minutes. Cool completely in pan. Cut into 3- x 1 1/2-inch bars; remove from pan, and garnish each bar with a cherry half.