1. Prepare a covered grill for direct grilling. In a large bowl, combine sirloin, red onion, taco sauce, chili powder, cumin, ground coriander, garlic, salt, and pepper. Form 4 hamburger patties, about 4 inches in diameter. Grill patties 10 minutes, turning once after 5 minutes until an instant-read thermometer inserted in the side of each burger registers 160 degree F. Place buns on the grill just long enough to toast slightly. Place each burger on a bun and top with shredded iceberg lettuce and shredded Cheddar cheese. Makes 4 servings.