Dry-Rubbed Ribs with Macaroni Salad

Bring a medium pot of water to a boil and heat the grill to medium. In a small bowl, combine the sugar, garlic powder, paprika, 1/4 teaspoon cayenne and 1/2 teaspoon salt. Rub the spice mixture on the ribs. Place the rack on the grill bone-side down and grill, covered, for 20 minutes. Turn and grill, covered, until cooked through, 5 to 10 minutes more. Transfer to a cutting board and cut into pieces. Meanwhile, add the pasta to the water and cook according to package directions. Drain and run under cold water to cool. In a large bowl, whisk together the mayonnaise, vinegar, pinch cayenne, and 1/4 teaspoon each salt and pepper. Add the pasta and toss to coat. Fold in the scallions, celery, and parsley. Serve with the ribs and corn on the cob, if desired.