mix ground round, grated cheeses, egg, and liquid smoke.
separately mix broth cube with hot water and bread crumbs with gluten and spices.
add powders and broth to ground round mix. it should be about the consistency of raw meatballs. line a 9" square or 13"x9" pan with parchment paper (don't just grease, it will stick anyways), preheat the oven to 350f.
spread the meat mix into the pan 1/2" thick, if using the bigger pan it may have a gap on both sides, that's fine. pierce with a fork to mark your diving lines for the 12 square patties. sprinkle the onions on top and press down lightly.
bake at 350 for 20 min, add remaining cheese and pop back in oven for 5 min.
spread the buns with ketchup on one side, mayo on the other, top each with a patty, close up the buns and enjoy!