Heat 1 tablespoon vegetable oil in a non-stick pan. Add chopped onion and sweet peppers and sauté until soft, about 2 to 3 minutes. Remove and set aside to cool.
Place ground beef in a large bowl. Add salt, ground pepper, chipotle pepper, cumin, and sauté onion and sweet peppers. Mix well.
Divide into 4 portions. Shape into a patty. Flatten the patty and place a slice of folded cheese in the middle. Wrap the meat around the cheese. Again shape into a patty with the cheese in the middle. Repeat with the remaining 3 patties.
Place a skillet on the stove over medium heat. When skillet is hot, add just a thin coating of oil. Transfer meat patties to the skillet and allow them to cook for 4 to 5 minutes on each side turning once.
To serve, split a hamburger bun in half. Place a piece of lettuce on the bottom half of the bun followed by a meat patty, onion, and a slice of tomato. Top with the other half of the hamburger bun. Enjoy!