Preheat grill to medium high heat using 2 burners.
1. Add ground beef to medium sized bowl. Add 1 tsp. each salt and ground pepper. Blend well and portion beef into 4 equal balls.
2. Form balls into patties. Using your fingers, create a small dimple in one side of each patty. This will help reduce shrinking while cooking.
3. Place patties, onion rings and peppers on separate burners on the preheated grill. Start with peppers skin side up.
4. Halfway through cooking, flip the patties.
5. Halfway through cooking, flip the onions and peppers to allow them to char and become soft.
6. Remove patties from heat and top with cheese to melt; allow to rest.
7. Remove onions and peppers from heat. When cool enough to touch, slice peppers into strips and onion rings in half to create half-moons.
8. Assemble the burgers: Place patties on buns and top with onions and peppers. Drizzle with 1-2 Tbsp. Frontera Classic Fajita Sauce and top with buns. Enjoy!