Preheat the oven to 350 degrees F (175 degrees C). Butter a 9-inch casserole dish.
Bring a large pot of lightly salted water to a boil. Cook elbow macaroni in the boiling water, stirring occasionally, until tender yet firm to the bite, about 8 minutes. Drain.
Combine macaroni, salmon, cream of mushroom soup, 1/2 can of milk, Parmesan cheese, salt, and pepper in a casserole dish. Mix until well blended. Sprinkle French-fried onions on top.
Bake in the middle rack of the preheated oven until lightly browned on top, about 30 minutes.
