Lvl 45-50 food vendors?

[Vidu]

Quite frankly, the best bonus you get from food at that level is the +3% exp and thats on any food, so you can just eat basically whatever gives you the buff (even just some fruit).

The other food-buffs only get intresting when it comes to raiding - and then you want crafted food anyways, because (1) vendors dont sell HQ-food (which has better stats than the NQ-version you get from vendors) and (2) the "good" food isnt sold by vendors.

If you really, really want some food with stats though, I'd recommend using Mustard Eggs (you can buy these in the South Shroud, at 17,)/19,7 from the Alehouse Wench) or Antelope Steak (from the same vendor). There are some "better" options once you reach Ishgard, but I'd like to repeat that it doesnt make a huge difference, no one will be mad at you for not using food during leveling dungeons and the most important bonus is the exp anyways (which you'll get from pretty much anything).

[Iscah]

Antelope Steak (from the same vendor)

IIRC that's an item you get as a quest reward at some point so there might be an overstock if them on the marketboard.