SMASHING PATTY WITH CONFIDENTIAL SAUCE

Ingredients
One tablespoon of olive oil
2 cups thinly sliced onion from 1 large onion
Six tablespoons unsalted butter, divided Garlic powder, and kosher salt
ketchup, 2 tablespoons
1 and a half kilos of lean ground meat
2:1 Worcestershire sauce
8 slices rye bread
Onion powder, 1/2 teaspoon
About eight ounces of sliced Swiss cheese