Pour tomatoes into a roasting tray and bake in the oven at 160 degrees for about an hour or until the tomatoes are dry on top. Remove tray from oven and crush tomatoes with a potato masher. You don't want to puree them, just break them into even pieces.

In a heavy-based pot, heat the butter until it turns nut brown, then add the tomato - be careful as it may spit a little. Season then simmer for a few minutes. Remove from heat; you don't want to overcook it