Gayathri's Cook Spot, which did the trick.
For the lime Cupcakes, i just did the above recipe (but you can use a boxed cake or your own recipe) and added the zest from 2 limes and 1/2 lime juiced. The real find was the frosting. I had to figure out how to make the frosting firm (and again... no butter), and the trick is to use egg whites. You beat them until they peak and then add the vanilla and powdered sugar (2 egg whites, 4 cups powdered sugar, 1 tsp vanilla). you can add milk if you need more moisture. The frosting hardened, just on the outside, pretty quick and allowed me to put the fruit in the middle.