Pour batter into 2 lightly greased parchment paper-lined 15- x 10-inch jelly-roll pans.
Bake and cool as directed in "Pick a Pan," below. Do not remove cakes from pans.
Spread top of 1 cooled cake (in pan) with spreadable fruit. Invert remaining cake onto fruit-covered cake. Remove top pan. Remove and discard top piece of parchment paper. Cover and freeze cake 1 to 2 hours.
Run an offset spatula under and around sides of cake to release from pan. Invert cake onto a cutting board. Remove and discard remaining piece of parchment paper. Trim and discard edges of cake. Cut cake into 32 squares.
Tint Vanilla Buttercream Frosting with desired amount of food coloring, and beat until blended. Place in a zip-top plastic freezer bag (do not seal). Snip 1 corner of bag to make a small hole. Pipe frosting onto each cake square. Garnish, if desired.
*Seedless jam may be substituted.
Pick a Pan:
These batters can be baked in many different pans. Follow our guide below for perfect layers every time. As usual, be sure to test the cakes for doneness by inserting a wooden pick into the center. It should come out clean.
Bake at 350 in 2 greased and floured (9-inch) round cake pans 32 to 36 minutes. Cool as directed.
Bake at 350 in 2 greased and floured (8-inch) square pans 30 to 34 minutes. Cool as directed.
Bake at 350 in 2 lightly greased parchment paper-lined (15- x 10-inch) jelly-roll pans 15 to 17 minutes. Cool in pans on wire racks 30 minutes.