Bring 6 quarts water and 1 teaspoon salt to boiling in large saucepot over high heat. Gradually add tortellini and onions. Reduce heat to medium-high; boil gently 7 to 9 minutes or until tortellini is firm but tender and onions are crisp-tender.
Meanwhile, heat oil in medium-size skillet over medium heat. Add garlic; cook until lightly golden, about 2 minutes. Transfer to food processor along with red peppers, tomato juice, tomato paste, vinegar, hot-pepper sauce and remaining 1/2 teaspoon salt. Whirl until peppers are pureed.
Drain pasta and onions; turn into large bowl. Pour sauce over top; add olives and parsley; toss. Serve with Parmesan if desired. Makes 6 servings.