Cook pasta according to package directions, omitting salt; drain. Return pasta to pan; cover and keep warm.
Meanwhile, in a large skillet heat oil over medium-high heat. Add onion; cook for 2 to 3 minutes or until tender, stirring occasionally. Add garlic; cook and stir for 1 minute. Add tomatoes; cook and stir about 2 minutes or until heated through. Add spinach and basil; cook and stir for 1 to 2 minutes more or just until spinach is wilted.
Add tomato mixture to pasta; toss gently to combine. Transfer mixture to a warm serving platter. Top with chicken and cheese.