Basil Pesto Pomodoro Sauce

Spray large skillet with cooking spray. Heat over medium-high heat. Add onion; cook and stir 5 minutes, or until tender. Add tomatoes and simmer 5 minutes, or until slightly thickened. Stir in pesto just before serving. Serve with 1 pound dry pasta (such as fusilli, spaghetti or penne), cooked according to package directions. May also be served over cooked chicken breasts or fish.