Prepare Icing We suggest that you tint all icings at one time while cake cools. Refrigerate tinted icings in covered containers until ready to use.
Make 4 1/4 cups buttercream icing: Tint 1/2 cup violet
Tint 1/4 cup yellow
Tint 1/2 cup rose
Tint 1/4 cup orange
Tint 1/4 cup blue
Reserve 2 1/2 cups white (thin 1 3/4 cups with 1 1/2 Tablespoons light corn syrup) Ice smooth with thinned white icing
Decorate in Order
1. Ice cake smooth with thinned white icing.
2. Fill disposable decorating bag with rose icing, cut 3/8 in. diameter opening in bag, and pipe icing on top tier of cake.
3. Fill disposable decorating bag with yellow icing, cut 3/8 in. diameter opening in bag, and pipe icing on middle tier of cake.
4. Fill disposable decorating bag with violet icing, cut 3/8 in. diameter opening in bag, and pipe icing on bottom tier of cake.
5. Use tip 21 and white icing to pipe shell bottom border on all "tiers."
6. Use tip 3 and orange and blue icing to print message on cake.
7. Sprinkle icing on tiers with rainbow nonpareils.
Baking Instructions Preheat oven to 350°F or temperature per recipe directions. Your cake will unmold easily, without sticking, when you prepare the pan properly. Grease the inside of pan using a pastry brush and solid vegetable shortening (do not use butter, margarine or liquid vegetable oil). Spread the shortening so that all indentations are covered. Sprinkle about 2 Tablespoons flour inside pan and shake so that flour covers all greased surfaces. Turn pan upside down and tap lightly to remove excess flour. If any shiny spots remain, touch up with more shortening and flour to prevent cake from sticking. (You can use vegetable oil pan spray or vegetable oil pan spray with flour, in place of solid shortening and flour or use Wilton Cake Release, for perfect, crumb-free cakes!).
Make one 2-layer cake mix according to package or recipe directions. Pour the cake batter into pan, and if necessary, spread the batter around with a spatula to fill all areas of the pan evenly. Be careful not to touch sides or bottom of pan. Bake cake on middle rack of 350°F oven for 30-40 minutes or until cake tests done according to recipe directions.
Remove cake from oven and cool on cake rack for 10 minutes. While the cake is still in the pan, carefully slice off the raised center portion of the cake. This allows the cake to sit more level and helps prevent cracking. To remove cake from pan, place cooling rack against cake and turn both cake rack and pan over. Lift pan off carefully. Cool cake at least one hour. Brush loose crumbs off cake.
To transfer cake to serving board, hold a cake board against cake and turn both cake and rack over. Lift off rack. Hold another board against bottom of cake and turn cake over. Be sure to hold cake, rack and board close together while turning to prevent cake from cracking.
We recommend hand washing pan in hot, soapy water.