1 pound ground round
1 cup chopped seeded plum tomato
1/4 cup minced fresh cilantro
1 tablespoon chili powder
2 teaspoons minced seeded jalapeno pepper
1/2 teaspoon salt
1/2 teaspoon dried oregano
1/2 teaspoon ground cumin
1/4 teaspoon pepper
4 (3/4-ounce) slices reduced-fat Monterey Jack or cheddar cheese
1/4 cup fat-free sour cream
4 (1 1/2-ounce) hamburger buns
4 iceberg lettuce leaves
8 (1/4-inch-thick) slices tomato
Grilled onions (optional)
Combine first 9 ingredients in a bowl; stir well. Divide mixture into 4 equal portions, shaping into 1/2-inch-thick patties.
Prepare grill. Place patties on grill rack coated with cooking spray; grill 6 minutes on each side or until done. Place 1 cheese slice on top of each patty; cover and grill an additional minute or until cheese melts.
Spread 1 tablespoon of sour cream over top half of each bun, and set aside. Place patties on bottom halves of buns; top each with lettuce, tomato, onions (if desired), and top half of bun.