@carly you should always cook onions right down, at least until golden (20 mins minimum). Undercooked onions are a cardinal sin in any form of cooking!
I don’t know how to cook curries at all, and I want to cook a slow-cooked beef or lamb curry for tonight. When I look at recipes, they all sound horribly wrong to me. They involve things like covering the raw meat in yoghurt and then putting that, cold, into a simmering sauce. The image that this conjurs in my head is not something I want for dinner. This runs against all my instincts, which would tell me to sear the meat with spices, put that into a simmering sauce for a few hours, and add yoghurt just before serving.
I have cooked one or two recipes that go like this. The recipes never sound appetising and often they don’t look that promising during the cooking process – however there are one or two curries of this style that have become my favourites so I would encourage you to give it a go even if you never do it again.