Cinnamon, dash optional Preheat oven to 350 degrees F.(moderate) Grease and flour two or three 8 inch layer pans or one 9x12x2 cake pan. Mix all dry ingredients together. Blend in mayonnaise, eggs, vanilla and 1/2 of sour cream. Beat 2 minutes at medium speed with mixer or 300 strokes by hand. Add remaining sour cream and beat 2 minutes longer. Pour into pans. Bake 25 to 35 minutes until a toothpick inserted in center comes out "clean". Cool on rack a few minutes before removing from pan. When cool, frost cake! FROSTING: Cream butter and cream cheese together until fluffy, gradually add dry ingredients one at a time until all are well blended. Add vanilla and blend well.