Heat butter and olive oil in skillet until sizzling. Add the onions a couple of handfuls at a time and stir until soft and starting to turn translucent, 1-2 minutes. Add more onions and continue until you’ve added all the onions. Season with a pinch of salt. Reduce heat and cook onions, stirring every few minutes until blond colored, 15-20 minutes.
Divide the meat into patties and place on plate, using two fingers, gently press the center down slightly. This ensures that the burgers don’t shrink to much.
Sprinkle with salt, pepper and garlic powder on both sides.
Cook burgers on the grill to desired doneness. The time will depend on the thickness of your burgers. Add cheese and cook until cheese is melted.
Serve on soft buns with prepared Chipotle Dip mix. Top with caramelized onions, lettuce and tomato, if desired.