Separate eggs. Allow egg whites to stand at room temperature for 30 minutes (reserve yolks for another use). Meanwhile, grease one 92-inch round cake pan. Line bottom of pan with parchment paper. Grease parchment paper and lightly flour pan; set aside. In medium bowl stir together flour, baking powder, baking soda, and salt; set aside.
Preheat oven to 350 degrees F. In large mixing bowl beat butter with electric mixer on medium to high for 30 seconds. Add sugar and vanilla; beat until well combined. Add egg whites all at once; beat on medium-high 3 minutes. Alternately add flour mixture and buttermilk to butter mixture, beating on low after each addition just until combined (batter may look slightly curdled). Transfer batter to prepared pan.
Bake in preheated oven 35 to 40 minutes or until a wooden toothpick inserted near centers comes out clean. Cool cake in pan on wire racks 10 minutes. Remove from pan. Cool completely on wire rack.
Frost top and sides of cake with Vanilla Sour Cream Frosting. Arrange berries around outside edge of cake to resemble a wreath. Heat strawberry jelly until melted; brush evenly over berries.
Line a small baking sheet with wax paper. Place melted candy coating in a heavy resealable plastic bag; snip a small hole in one corner of the bag. Pipe candy coating onto the prepared baking sheet to form 3- to 4-inch bow(s). Let stand until set (if necessary, place in the refrigerator until set). Carefully lift bow(s) off paper and transfer to cake.
Vanilla Sour Cream Frosting
In large mixing bowl combine butter, sour cream, and vanilla. Beat with electric mixer on medium for 30 seconds. Gradually beat in powdered sugar. Thin with buttermilk or milk to desired consistency. Makes about 4-1/2 cups.