Cook macaroni according to package directions, adding broccoli during the last 3–4 minutes; drain.
In a large saucepan, melt butter. Stir in the flour, garlic powder, onion powder, pepper and salt until smooth; gradually stir in the evaporated milk. Bring to a boil; cook and stir for 2 minutes or until thickened. Remove from the heat; stir in 2 cups cheese.
Place half of the macaroni and broccoli in a greased 13-by-9-inch baking dish. Top with half of the cheese sauce. Repeat layers. Sprinkle with cracker crumbs and remaining cheese.
Bake, uncovered, at 375 degrees for 20–25 minutes or until bubbly.