Heat oil in a large nonstick skillet over medium-high heat; add onion. Cook 2 minutes, stirring frequently. Add plum tomatoes, salt, black pepper, and red pepper. Reduce heat and simmer 8 minutes, stirring occasionally.
Cook pasta according to package directions, omitting salt and fat. Drain into a sieve over a bowl; add sun-dried tomatoes to reserved pasta water. Let stand 10 minutes; drain. Combine pasta and sun-dried tomatoes.
Combine pasta mixture and plum-tomato mixture in a large bowl; stir in 3/4 cup cheese, olives, and parsley. Divide pasta evenly among 4 bowls; garnish each with 2 tablespoons Parmesan.