Tomatoes are perfectly acceptable for rabbits to eat; it is just the stems and leaves which you will want to avoid giving to them. Rabbits love leafy greens and vegetables, so you will want to provide them with as much of these foods as possible in order to keep them healthy.
Before you feed your rabbits any tomatoes at all, you will need to make sure that the stems and leaves have been removed, because they can cause problems like diarrhea along with serious health problems which will prevent them from staying as healthy as possible. You should also remember to not feed your rabbits too many tomatoes at one time and to include lots of leafy greens in their diet.