Gluten is a binder that is found in grain products such as wheat and flour. Since no fruit or vegetable contains any type of grain product, it is very safe to say that the person that chooses to eat a gluten-free diet can eat most any fruit or vegetable–without having to worry much.
While tomatoes are a gluten-free food, it is possible that different ingredients are added to sauces that contains tomatoes and they can include fillers or binders that may also include wheat. Since that is the case, the person that chooses to eat a gluten-free diet has to make sure that they are thoroughly reading the ingredient labels to make sure that there is no wheat contained any of their food or sauces.