1. Preheat oven to 350 degrees. Line two 6-cup jumbo (1 3/4-inch deep, 4-inch diameter) cupcake pans with baking cups, and set aside. In a medium bowl, sift together flour, baking powder, and salt; set aside.

2. In the bowl of an electric mixer fitted with the paddle attachment, cream butter and sugar on medium speed until light and fluffy, about 3 minutes. With the mixer set on medium, add eggs, one at a time, then vanilla.

3. With the mixer on low speed, add one-third of the reserved flour mixture, and mix until combined. Add 1 cup buttermilk, and mix until combined. Add another third of flour mixture, then the remaining 1/2 cup buttermilk. Add the last third of flour, and mix until smooth.

4. Divide batter among cups, and bake until golden, about 30 minutes. Transfer muffin tins to a wire rack to cool. Remove cupcakes from tins.

5. To decorate, frost each cupcake with 3 tablespoons Seven-Minute Frosting. Place sprinkles in a shallow bowl. Fill a small, shallow bowl with cream-colored sprinkles and another with green sprinkles Gently press each frosted cupcake into the sprinkles, rolling the cake around so the entire surface is coated. Alternate colors so that you have 6 green and 6 cream-colored cupcakes.

6. For flowers, use a 2 to 2 1/2-inch gum-paste petal cutter to cut petals from the jellied citrus and grapefruit slices -- you will need 72 petals. Using scissors or a sharp knife, cut off the lower one-third of 12 large gumdrops, and discard. Gently press a gumdrop into the center of each cupcake, and arrange 6 jellied petals around each gumdrop to form a flower. Place the cupcakes around the larger cake on the cake stand.