Personally, I would simply use "manger" (at least, that's what I ask my husband when I see him in the evening).
"prendre" in this case seems to be more about what you took/chose (in a restaurant). For instance, you recommended a restaurant to someone and wondered what they took (the fish as opposed to the meat or whatever?).
I think it's fairly common to use prendre when talking about breakfast ("Tu as pris quoi ce matin au petit-déj’ ?"). When talking about lunch, however, it suggest that you think the person you're talking to had lunch in a canteen/cafeteria, or perhaps they got something from the supermarket. When it comes to dinner, though, it sounds straight-up bizarre to me (unless it's clear the dinner was had in a restaurant). I would be more likely to ask "Tu t'es préparé quoi pour le dîner (ce soir) ?" ou "Tu as mangé quoi au dîner hier soir ?".