Slice the onions very thin and sprinkle with 1 tsp salt
You’ll place the onions in a colander and let drain for 30 minutes.When you’re ready to cook the burgers, squeeze the onions even more dry with paper towels.
Melt the butter in your skillet. I always add a bit of oil so that the butter won’t burn.
Divide the meat into 4 equal pieces.
Divide the onions into 4 piles. Smoosh the hamburger meat into each onion pile.
Fry each burger over medium heat until the onions are dark and caramelized.
You’ll turn them over and cook them well on the other side until done.