Have gone to a pizza place and asked for it as an unpizza without the dough, and I have also ordered pasta that way with extra veggies.
Some places will let you order roman leafs in stead of tortilla for fajita and some sandwich place do this too instead of buns.
Don’t be afraid to ask for what you want and how, you are the one eating it and paying for it. Also, like one of my friends stated when you order a burger or sandwich without the bun you can explain to them how much more they are really making for as profit.
Hope this help, and have a good time on your trip.