Is tomato a common noun or proper noun?

The noun 'tomatoes' is a common noun, the plural form of the noun 'tomato'; a general Word for a type of fruit (often prepared as a vegetable) that has many varieties; a Word for any tomatoes of any kind.

A proper noun is the name or title of a specific person, place, or thing; for example, Hot Tomatoes Neapolitan Pizza(shop) in Pittsfield MA or "Attack of the Killer Tomatoes" (1978 movie).