Some categorizations we struggled with and this was one of the worst. Yes, we know tomatoes are a fruit but we didn't expect people would look there. They are in Vegetables, Salad.
If you ever cannot work out which filter category an ingredient is in, the tip is to enter the word in the search box then look for the filters with the highest number. In this search of the Library Online Recipes you will see Vegetables has the highest number against it, then Salad has the highest when you drill down.