It is safe but do not expect too much
Burger king decided to help us and that's great. In any restaurant (most probably across the globe) you can ask for gluten free and they will prepare their meat with anything you ask (salad) except bread (or other gluten ingedients). You get it in the salad container.
With some french fries besides it works.
The only thing about Aviles - like in many other places English is really strange for them. Use your hands and other gestures. :) But stay polite, it's still food.
gluten free, aviles, spain