Preheat oven to 350 F. Spray non-stick cooking spray in a 3-quart or so container. Melt butter in a large skillet. Saute onion and pepper until tender. Meanwhile, cook pasta according to package directions, then drain. If not using pasta immediately, rinse a couple of times in cold water before draining to prevent further cooking. Empty the large can of whole tomatoes (with juice) in a bowl and coarsely chop them so that each tomato is in 3 or 4 pieces and much of the juice is released. In a large mixing bowl, mix the onions & peppers (with butter), all the tomatoes and juice, the shredded cheese & fold in the pasta until mixed well. Pour into your baking container and bake at 375 F. for 1 hour, uncovered.