Pour 4 to 6 quarts of water in a large pot and put it on the stove. Position the stove burner to medium high and bring the water to boil. Also add a pinch of salt and one tablespoon of oil to the water.
Once water starts boiling, add the macaronis and give it a good stir. Allow the macaronis to cook in boiling water for almost 8 minutes or until they are al dente.
Place a strainer in the sink and carefully run the pasta and water through it.
Once the water has completely drained, transfer the macaronis to a large bowl.
Add cream of mushroom soup and frozen peas to the macaronis and stir gently to mix the ingredients well.
Also add tuna chunks properly to this mixture, making sure you do not mash boiled macaronis.
Apply a little quantity of butter on a baking dish and transfer the mixture to it.
Spread the macaronis evenly with a spoon and top them with one cup finely shredded cheddar cheese and French fried onions.
Put the baking dish in the oven preheated at 375 degrees Fahrenheit and bake for 12 to 15 minutes, or until the cheese melts.