How to Make It
Combine all ingredients in a bowl and set aside for 1 hour at room temperature.
Combine the ancho powder, onion, garlic, chipotles and orange juice in a blender and blend until smooth. Slowly add the olive oil and blend until emulsified. Place the lamb in a shallow baking dish, cover with the marinade and let marinate for 1 hour. Heat the grill. Season the lamb with salt and pepper and grill for 3 minutes on each side for medium-rare. Let sit 10 minutes before slicing thinly.
For each taco, lay four slices of lamb over 1/2 of the tortilla, sprinkle with 2 tablespoons each of the Jack and cheddar cheeses and 1 tablespoon of the feta cheese. Top with grilled onion and mint. Season to taste with salt and freshly ground pepper. Fold over the tortilla and brush with olive oil. Grill for 3 minutes on each side or until crispy and the cheese has melted. Serve with the Tomato-Mint salsa.