Preheat oven to 400 degrees. Lightly oil 2 eight inch square baking dishes or other shallow dishes. Boil noodles according to directions, drain and return to pot.
In a dutch oven, heat oil over medium heat. Add peppers and season with salt and pepper to taste. Cook until tender. Add the flour and cook for 1 minute while stirring. Gradually add the milk, stirring till smooth. Cook till it comes to a simmer.
Remove from heat and add to noodles in pot along with the tuna, artichoke hearts, half the cheese and onion/scallion. Toss well. Divide between baking dishes or one large dish. Sprinkle with rest of parmesan and bake till golden and bubbling. Around 20 minutes.