I had a bit of leftover vanilla buttercream in the freezer I wanted to use up (the stuff keeps for months when you freeze it- I often make more than I need, and collect any leftovers). I decided to get creative and try making raspberry buttercream: I put a punnet of fresh raspberries into a saucepan, heated them until they broke down into liquidy bits, sieved them and boiled down the clear juice until thick. Then I cooled it, and whipped it into the defrosted buttercream (there was about a coffee mug-sized amount of leftover buttercream to work with).
I baked some lemon cupcakes using my bog standard sponge recipe, omitting the vanilla and adding the juice and zest of a lemon, and frosted them with my raspberry buttercream.
It was a fruity, zingy success.