preheat oven to 350F. Put pasta on to cook, drain and set aside when done. Chop the asparagus into 1 inch long pieces.
heat oil in large skillet. While this heats, coarsely chop bell peppers and onion. Add these to the hot pan, cook on medium high until tender then add seasoned flour and pepper. Mix well, add milk all at once. Cook, stirring often, till it begins to thicken up a little. Add the grated cheese and asparagus, stir until cheese is melted. Add lemon juice and crumbled salmon, mix in with reserved pasta.
pour into a 2 quart baking dish. Sprinkle with bread crumbs and bake, uncovered, for ~ 30 minutes or until heated through and topping is golden. Let dish rest for about 10 minutes before serving