Heat a large skillet over medium heat and cook the ground beef with the chopped onion until the meat is browned and the onion is soft.

Once cooked, add the Rotel tomatoes and taco seasoning, stirring to combine all the flavors.

In a separate pot, prepare the spaghetti according to package instructions until al dente.

After draining the spaghetti, add it into the skillet with the meat mixture.

Pour in 2 cups of water and stir until everything is well mixed.

Let it simmer for 5-10 minutes until everything is heated through and the flavors meld.

Serve hot, with shredded cheese on top if desired.