Preheat oven to 350 degrees.

Butter a 1 1/2- quart casserole dish. Set aside.

In a large saucepan, bring 3 quarts water to a boil. Cook macaroni in boiling, salted water until tender, according to package directions. Drain.

While the pasta is cooking, melt butter in a large skillet or saucepan. Add onion; cook until soft.

Blend in flour and milk.

Cook, stirring constantly until thick.

Add salt, pepper and cheese. Heat and stir until cheese is melted.

Add the drained macaroni to the thickened cheese sauce. Stir to combine.

Pour into buttered casserole.

Sprinkle with additional cheese and paprika.

Bake 30 minutes at 350 degrees or until bubbly and browned.