How to Make It
Cook egg noodles according to package directions, adding green beans to the cooking water during the last 3 minutes of cooking time. Drain and rinse thoroughly with cold water to stop the cooking process.
Melt butter in a large Dutch oven over medium-high heat. Add flour, and cook, whisking constantly, 1 minute. Slowly whisk in milk, and cook, whisking constantly, about 5 minutes or until mixture comes to a boil and thickens. Remove from heat, and slowly whisk in 1 cup Parmesan, whisking until smooth. Whisk in salt and pepper. Add noodles and green beans, parsley, tuna, capers, and, if desired, olives; gently toss to mix well. Add tomato, and gently toss to combine. Transfer mixture to an 11- x 7-inch (1 1/2-quart) baking dish coated with cooking spray.
Cover and refrigerate overnight, or sprinkle remaining 1/4 cup Parmesan over casserole, and bake at 375° for 30 minutes or until bubbly and heated through. Let stand 5 minutes before serving.