In a mixing bowl, combine the ground lamb, chopped onion, minced garlic, breadcrumbs, egg, ground cumin, ground coriander, paprika, salt, and pepper. Mix everything together until well combined.
Divide the mixture into 4 equal portions and shape them into burger patties. You can make them as thick or thin as you prefer.
Preheat your grill or a skillet over medium-high heat.
If using a grill, oil the grates to prevent sticking. If using a skillet, add a little oil to the pan.
Place the lamb burger patties on the grill or in the skillet. Cook for about 4-5 minutes per side for medium-rare burgers, or adjust the cooking time according to your preference for doneness.
While the burgers are cooking, you can toast the burger buns on the grill or in a toaster.
Once the lamb burgers are cooked to your liking, remove them from the heat and let them rest for a few minutes.
To assemble the burgers, place a lettuce leaf on the bottom half of each bun, followed by a lamb patty. Add tomato slices and red onion slices (if desired). Top with a dollop of tzatziki sauce or your favorite condiments.
Place the top half of the bun on top of the condiments to complete your burger.
Serve your homemade lamb burgers immediately with your favorite side dishes, such as fries or a salad. Enjoy!