In a large bowl mix together ground beef, lime juice, garlic, onion and tomatoes. Form meat into 6 patties.
Cook burgers to desired doneness on a preheated grill. Add a slice of cheese to each burger during the last minute of cooking.
Serve on toasted buns with a healthy dollop of guacamole.
This recipe also makes great sliders. For a leaner version, use ground turkey instead of ground beef.