Lamb Burgers with Romesco

For Romesco sauce: Toast almonds in a dry skillet over medium until lightly browned and fragrant, about 4 minutes. Coarsely chop almonds; place in a food processor and let cool. Add roasted red peppers, tomato, bread, 1/2 teaspoon kosher salt, the vinegar, whole garlic clove, sugar, paprika and cayenne pepper. Pulse until large ingredients are broken down. With the motor running, slowly add olive oil and process until sauce is smooth enough to spread but still has a rustic texture. Taste; add additional salt or vinegar if needed. Transfer to a bowl. Cover and chill until needed. (Romesco sauce may be stored in an airtight container in the refrigerator up to 5 days.)

For burgers: Grate half of the red onion. In a large bowl, combine grated onion, the lamb, minced garlic, cumin, coriander and 1 teaspoon kosher salt; mix gently with your hands. Form mixture into six loosely packed balls, each weighing approximately 5 ounces. (Packing the meat too tightly can result in tough burgers.) Gently flatten the balls into patties slightly wider than the buns. Create a divot in the centers of the patties with your fingers, so that burgers remain flat and do not shrink when cooked.

Create hot (direct) and cooler (indirect) zones in your grill, preheating the hot zone to high. Place burgers on grate over indirect heat. Cover and grill burgers until internal temperature reaches 140°, 20 to 25 minutes,turning once halfway through grilling. Move burgers over direct heat in hot zone of grill. Grill until internal temperature reaches 160°, 5 to 8 more minutes, turning once. Transfer burgers to a plate.

Slice remaining half of the red onion. To assemble burgers, spread goat cheese (if using) on bottom buns. Top with burgers, sliced onion and arugula. Spread Romesco sauce on top buns; place on top.