1/2 tablespoon unsalted butter, with a splash of vegetable oil (so the butter won’t burn)
1 box WHITE cheddar macaroni and cheese (not the neon orange stuff)
1/2 onion, chopped (about 1/2 cup)
1 (6-ounce) can solid white albacore tuna, drained
2 tablespoons unsalted butter
1 cup skim milk
1 cup saltine cracker crumbs
1 cup cheddar cheese, low-fat, shredded

Preheat oven to 350 degrees. Boil water to make boxed mac and cheese. Cook pasta and drain.
In the meantime, chop your onion, open and drain your tuna, lightly grease a 2 quart casserole dish and get ready to launch into tuna casserole land.

In the same pot you cooked your pasta, melt your 1/2 tablespoon of butter, with a splash of vegetable oil. Now sauté your onion and as it turns clear, add the drained tuna. Then add the milk, 2 tablespoons butter and sauce packet from the box and cook till it thickens. Schlep everything together except the saltines and cheddar and stick in your prepared casserole dish. Top with saltines and then the cheese. Bake for about 15 minutes, give or take, until the cheese is nice and bubbly on top.

Recipe from Leanne Ely at Saving Dinner. There are recipes galore over there.