Preheat oven to 350°F.
In a big skillet, add the bottom beef and onion over medium-high warmth and brown the bottom beef, breaking the meat aside nicely because it cooks.
Drain grease, if wanted, then add bouillon dice, water, brown sugar, apple cider vinegar, and Worcestershire sauce. Deliver to a boil, then scale back warmth and let simmer till liquid has evaporated.
Place bottoms of the buns in a baking dish, and prime with beef combination. Place pickles on prime, adopted by cheese slices, and prime with prime of buns.
In a small bowl, whisk collectively melted butter, brown sugar, Dijon mustard, and Worcestershire sauce and brush over buns.
Cowl baking dish with foil and bake 25 minutes. Take pleasure in!
