does anyone here sell their cakes in restaurants...if so can u give me tips on how to do it and what to do

Are you licensed? Restaurants are not going to accept cakes from an unlicensed bakery.

Depends on the restaurant. My DD is a waitress on weekends at a very upscale restaurant in MA. They buy their Carrot Cake from an old woman that bakes them out of her home in RI. It's not legal in RI to bake out of your home. My DD has told this to the owner, he doesn't seem to be concerned, he claims she's been baking them for years for him.