2 Pastry bags; Ateco #10 round tip; Ateco #2 small round tip
Frost the cupcakes with the buttercream.
To pipe the flower: Place the grapefruit-tinted frosting in a pastry bag with a #10 round tip. Hold the bag straight above the cupcake. To create a 5-petal flower, start 1/2 inch from the edge, and squeeze and release while dragging toward the center of the cupcake to create a tear-shaped petal. Rotate the cupcake slightly after each petal.
Place the egg yolk-tinted frosting in a pastry bag with a #2 small round tip. Hold the bag straight up, and pipe a small dot into the center of the flower.