Mix all the spices into the ground lamb. Form into 2-ounce patties. Slice the red onions paper thin into half-moons and soak in a good amount of ice water to remove the sharpness. Pick and wash the cilantro. Mix the mayonnaise with the sumac.
Sear the lamb patties on medium to high heat and cook until medium. Split and toast the potato rolls. Place the patties on the roll and garnish with the sumac mayonnaise, red onion, and fresh cilantro.