Cook and drain noodles in a large pan. Leave noodles in the pan. In a medium sauce pan, melt the butter. Add the flour and stir. Add salt and pepper. Add the dried onion flakes. Stir in 2 cups milk until thickened. Stir in the cheese and mushroom soup. Fold in the tuna. Add the broccoli to the noodles then stir in the sauce. Pour into a greased casserole dish. Top with French's Fried Onions. Bake at 350 degrees about 30 minutes or until hot and bubbly.