Juicy, grilled lamb burgers flavored with a Moroccan-inspired blend of garlic and spices and topped with fresh tomato, grilled onions and seasoned ketchup.
Preheat a gas or charcoal grill to a medium-high temperature (about 400°F).
Combine the ground lamb, tomato paste, garlic, salt, a few grinds of black pepper, cinnamon, cumin, coriander and onion powder in a shallow bowl. Use a wooden spoon to combine the meat ingredients as best you can before doing a final, gentle mix with your hands. Gently form the patties into quarter-pound portions and make a slight depression in the center of each with your thumb. Place on a plate and refrigerate for 15 minutes.
While the lamb burgers chill, make the sauce. Combine the ketchup, tomato paste, cinnamon, cumin and coriander in a microwave-safe bowl. Heat on 50% power for about 30 seconds - just long enough to warm the mixture slightly, then stir in the mint and set aside until ready to use.
Oil the grill grates, add the onion slices and grill until they're lightly browned and softened, about 1 minute per side. Transfer to a plate and set aside.
Oil the grill grates a second time, add the lamb burgers and grill until you see juices start to accumulate on the top of the meat, approximately 4 minutes. Flip the burgers and grill for an additional 3 minutes, or until they reach desired doneness (recommended internal temperature of 160°F). Transfer to a plate and let rest for 5 minutes.
To serve, add a slice of onion and tomato to the bottom half of each roll. Add a lamb burger and top with sauce.