Finely chop the onion.

In a skillet, cook the chopped onion in a small amount of shortening over medium heat until tender.

Add the ground beef to the skillet.

Cook the ground beef until it separates and changes color, ensuring it is fully cooked.

Add the peas and tomatoes to the skillet with the ground beef mixture.

Simmer the mixture for 20 minutes, allowing the flavors to meld.

Cook the noodles in salted water according to package directions until al dente.

Drain the cooked noodles thoroughly.

Preheat the oven to 350°F (175°C).

In a casserole dish, create alternate layers of the cooked noodles and the meat mixture.

Distribute the chunked cheese evenly over the top layer.

Bake in the preheated oven for about 1 hour, or until the casserole is heated through and the cheese is melted and bubbly.