Mix salt, pepper, oregano, and garlic pepper into the ground beef and form into patties that fit the shape of the buns. Store in the fridge until they're ready to be cooked.
Slice up the onion & green pepper.
Heat 1 Tbsp of butter in a pan on medium heat and then add onion. Cook at this for about 10-15 min until they start to caramelize. Pay close attention and stir occasionally to prevent them from burning.
Heat grill or pan for burgers.
Add green pepper to onions and cook for about 5 more minutes (adding additional butter if needed). Salt, pepper, and add red pepper for flavor. Cover or set aside in tinfoil to keep warm.
Add burgers to the grill and cook about 4 min on the first side.
Flip burgers and add cheese. Cook until you reach the correct temp (140F for medium), usually about 2 to 4 minutes
Add burgers to buns and cover with delicious pepper & onion topping. Enjoy!