Preparation

• Have ready 16 8-inch-long metal or wooden skewers. If using wooden skewers, soak them in cool water for 30 minutes before using.
• Cut two of the lemons into thin slices, and juice the third. Set aside.
• Prepare a medium (350°F to 375°F) gas or charcoal grill fire, and oil the grate. Using two skewers per kebab, thread the salmon, folded lemon slices, and asparagus onto the skewers, and arrange them on a large rimmed baking sheet. Brush the skewers with the oil, then season with salt, pepper, and pepper flakes; set aside.
• Whisk the mayonnaise, garlic, Worcestershire sauce, and 2 Tbs. of the lemon juice in a small bowl. Season to taste with salt and pepper. Grill the kebabs, turning once halfway through cooking, until the salmon and asparagus are cooked through, about 6 minutes. Serve with the aïoli for dipping.