How to Make It
Preheat a grill to medium-high (400°F to 450°F). Place potatoes in a large microwave-safe bowl. Cover bowl with plastic wrap; pierce once with a knife to vent. Microwave on HIGH for 5 minutes. Uncover and let potatoes cool slightly, about 5 minutes.
Cut steak with the grain into 16 to 24 (depending on length of steak) 1/2-inch-wide strips. Place steak in a medium bowl. Add 1 tablespoon oil, 1 teaspoon salt, and 1 teaspoon paprika; toss to coat.
Cut 1 bell pepper in half, and set aside half. Cut remaining 1 1/2 bell peppers into 24 (1 1/2- to 2-inch) pieces. Add bell pepper pieces and onion wedges to bowl with potatoes. Add remaining 3 tablespoons oil, 1 teaspoon salt, 1/2 teaspoon cayenne, and remaining 1 1/2 teaspoons paprika; toss gently to coat.
Thread 2 to 3 steak strips (folded in half), 3 bell pepper pieces, 2 potatoes, 2 chorizo slices, 1 onion wedge, and 2 olives onto each of 8 (8-inch) skewers. Arrange kebabs and reserved bell pepper half on an oiled grill rack on preheated grill. Grill kebabs and bell pepper half, covered, turning occasionally, until steak is lightly charred and vegetables are crisp-tender, 8 to 10 minutes. Remove from grill; tent kebabs loosely with aluminum foil to keep them warm.
Peel charred bell pepper half, if desired; pat dry. Place bell pepper half in a mini food processor; process until finely chopped. Add mayonnaise, vinegar, garlic, remaining 1/4 teaspoon salt, and remaining 1/4 teaspoon cayenne pepper. Process until smooth. Serve sauce with kebabs.