1. Cook pasta according to package directions, omitting salt and fat. Drain and keep warm.
2. Heat a large nonstick skillet over medium-high heat. Remove casings from sausage. Add oil to pan; swirl to coat. Add sausage and onion to pan; cook 4 minutes, stirring to crumble sausage. Add garlic; cook 2 minutes. Stir in tomatoes; cook 2 minutes. Remove from heat; stir in pasta, 2 tablespoons cheese, salt, and pepper. Sprinkle with remaining 1/4 cup cheese and basil.