I'm looking for a long fic I read a while back.  It was based around an event like the Great British Bake-Off (only set in the US, obviously), and Dean is a contestant, so is Castiel who is an eccentric, super-rich loner (human, not an angel) and Dean takes an almost instant dislike to him.  However, through a series of mishaps and misunderstandings, they gradually get to know each other and get together.

Sam also features quite heavily in the story.

I seem to remember that this is an AU, in that I don't think Sam and Dean were hunters, al;though it's been a while and I could easily be wrong.