This rainbow fruity pebble cake is so much fun! Moist & perfectly sweet, with tons of crunchy fruity pebbles sprinkled all throughout! Don't forget the colorful frosting and sparkly gold glitter garnish!
Bake for 20 to 25 minutes, or until a toothpick inserted in the thickest part of the cake comes out clean or with a few moist crumbs.
Cool for 20 minutes, then remove the cakes from the pans and cool completely before filling and frosting with rainbow Swiss meringue buttercream.
To make the rainbow Swiss meringue buttercream and decorate the cake:
In a large glass or metal bowl, combine the egg whites and sugar.
Set the bowl over a pot of barely simmering water, and stir continuously, until the sugar is completely dissolved. (Check by rubbing a small amount between your thumb and forefinger; it should be hot to the touch, and feel smooth, not gritty.)
Remove the bowl from the simmering water and whip on high speed until the meringue is thick, white, glossy, and can hold stiff peaks. (It should be cooled completely. There should be no hint of warmth when you place your hand on the side of the bowl. Refrigerate the meringue for 15 to 20 minutes if necessary.)
Add the butter in, a tablespoon at a time, beating well after each addition. (If the mixture begins to look curdled, continue to beat until it comes back together, before adding the remaining butter.)