If you are ever in the Arlington Washington DC area please check out Liberty Tavern. They were amazing with my allergies(gluten and dairy) and took it so seriously. My burger came with the gf bun (no extra charge btw 🙌), but still had cheese on it. I alerted our server who promptly whisked it away and brought me back a separate (not-small and freaking delicious) side salad for me to eat while they had to remake the burger. Burger came out this time with just the bun and absolutely nothing else on it (and yet more ginormous side salad). I laughed and started eating it anyways and it was honestly the best tasting burger I've ever had, even plain (the gf bun was also perfectly toasted iykyk). Manager comes over and asks if they didn't put cheese on this time. I joke that they didn't take any chances and put nothing. He is very frustrated at this point and comes back with my lettuce/tomato/onion, and apologized again. Server comes back to make sure everything is good and tells me they're comping the burger because Manager was mortified that someone with an allergy might've had something that could've made them sick. As someone who has had less-than-stellar experiences with my allergies, I appreciated everything they did to make me feel like I wasn't a problem and to serve good food, which btw everyone we ate was amazing. Also I had zero reactions from the food.
We sat in the lower level tavern area since it was that weird happy hour period before they serve dinner, had some great drinks and I loved the atmosphere. Our server noticed my husband watching a Lakers game on his phone, and put the game on a nearby TV for us (they bonded over Luka and Jokic since our server was from Serbia as well). If we're ever in the area again we'll definitely be going back.