Place beef, lamb and lemon juice in a large bowl. Gently combine until incorporated. Marinate in the refrigerator for 1 hour.Advertisement
Transfer the meat to a colander and press to squeeze out excess moisture. Place onion, garlic and olives in a food processor and pulse until coarsely chopped. Add to the marinated meat along with oil, cilantro, parsley, 1 tablespoon cumin, salt and pepper. Gently combine until evenly incorporated.
Position rack in upper third of oven; preheat broiler. Line a large rimmed baking sheet with foil and set a wire rack on it.
Using about 3 tablespoons of the meat mixture for each, form 12 thin patties, about 2 1/2 inches wide and 1/4 inch thick. Place on the wire rack.
Broil the patties until brown and cooked through, 8 to 10 minutes. Serve with additional cumin and harissa, if desired.
Ingredient note: Harissa is a fiery Tunisian chile paste commonly used in North African cooking. Find it at specialty-food stores, mustaphas.com or amazon.com. Harissa in a tube will be much hotter than that in a jar. You can substitute Chinese or Thai chile-garlic sauce for it.
3 1/2 medium-fat meat, 2 fat