In a large mixing bowl, combine the ground lamb, minced garlic, ras el hanout, ground cumin, paprika, salt, black pepper, and chopped cilantro. Mix gently until all ingredients are evenly incorporated.
Divide the mixture into four equal portions and shape them into patties, about 1 inch thick. Make a slight indentation in the center of each patty to ensure even cooking.
Preheat your grill or stovetop skillet over medium-high heat. Once hot, place the lamb patties on the grill and cook for 4-5 minutes on each side, or until they reach your desired doneness. The internal temperature should be around 70°C (160°F) for medium.
While the burgers are cooking, prepare the harissa mayonnaise. In a small bowl, mix together the mayonnaise, harissa paste, lemon juice, and preserved lemon rind until smooth and well combined.
Remove the burgers from the grill and let them rest for a few minutes. This allows the juices to redistribute.
Serve the lamb burgers on toasted buns, topped with harissa mayonnaise and your favorite garnishes, such as lettuce, tomatoes, or pickles.