I knew this place in Barcelona (% gluten-free) and we went to try it because we loved it. We arrived first and I took the opportunity to speak directly to the kitchen and clarify a comment I had read about gluten... it turns out that all the ingredients, sauces, fries, flours are gluten-free, with the exception of the hamburger bun... I saw the separate griddle on which it was made, they assured me that they would be careful with handling and it didn't seem very dramatic to me, since after all there was no one else and we were in a Fish and Chips place.
I am celiac and I did not have any symptoms, but in the hour and a half that we were there, I saw about 10 or 15 tables filled with hamburgers and only hamburgers... so, although Carmen and Jay have been very kind with their explanations and attention, I do not think that it can be considered a safe place for celiac people at all given the size of the kitchen and that there is only one person who spends the night handling bread