You can make casseroles and things like that without using onions and tomatoes or you can just hide them and probably the diners will never know. My husband hates all vegetables. He has no idea that he has been eating the following things for months:
onions, mushrooms, tomatoes, peppers, celery, carrots, sweet potatoes, courgettes, bean sprouts, cabbage, green beans, fennel, celeriac, swede, turnip, pumpkin and so the list goes on.
Most people unless they have an intolerance or allergy just don't like the tastes of the individual items but are unaware that they actually eat these things on a regular basis in soups and that most recipes using stock has these things in already. I chop things up very fine so that they cook down and just look like sauce when the dish is finished. If you need recipes to hide veg just e-mail and I can supply some.
Just make you favorite meals and omit what you don't like. I don't like mushrooms or black olives, so I make 1/2 w/o those items and 1/2 with, due to others liking them.