In a large skillet over medium heat, add the ground beef or turkey and cook for 5–7 minutes until browned and no longer pink. Use a wooden spoon to break apart the meat.

Stir in the taco seasoning and diced tomatoes to the skillet, letting the mixture simmer for about 2 minutes until fragrant.

Add the uncooked spaghetti to the skillet, pour in about 4 cups of water, cover with a lid, bring to a boil, then reduce heat to low and simmer for 10–12 minutes until the pasta is tender.

Remove from heat and gradually mix in the shredded cheddar cheese, stirring continuously until melted and creamy.

Spoon into bowls and add garnishes like sour cream, chopped avocado, or fresh cilantro.