Combine meat, Adobo, onion powder, pepper, and mustard. Mix with hands until just combined. Portion out and roll meat mixture into 12 balls (half mixture, next separate into fourths, then each fourth into 3 balls).
Arrange balls on the plate. Use a second plate to flatten into 1/2 inch tall patties.
Spray griddle with non-stick spray and preheat on Medium/Medium-High until hot. Cook the first side of the patties for 2 minutes, flip, immediately place on cheese, and cook for another 2 minutes (for well done, cook 3 minutes on each side). Set cooked patties aside.
Turn off the heat and remove excess grease (with a paper towel). Turn the heat back to Medium and add butter. Once butter is melted, place buns in butter – inside of bun down. Brush tops with melted butter. Cook on each side until lightly browned.