Heat oil in a large pot over high heat. Add the onion and pepper, cooking 3–5 minutes or until onion is translucent. Push veggies to edges of the pot.
Add beef in the center of the pot. Allow it to sear for about 1 minute per side, then break it apart with a wooden spoon as it cooks. Continue until beef is mostly browned with some pink remaining.
Mix in garlic, tomato paste, and taco seasoning. Season with salt and pepper; I add 1/4 teaspoon salt and 3/4 teaspoon pepper (see note 4). Stir and continue to cook until beef is fully browned through.
Add tomatoes, enchilada sauce, and chicken broth to the pot. Bring the mixture to a full boil.
Break spaghetti in half and submerge it in the liquid. Cook 10–12 minutes, stirring often and scraping the bottom of the pot to prevent pasta sticking. About 8–10 minutes in, reduce heat to medium to avoid evaporating too much liquid before pasta is done (see note 5 for troubleshooting).
Once pasta is al dente (slightly firmer than desired), remove the pot from heat. The dish should be quite saucy. Using tongs, toss the pasta for about a minute until the sauce thickens and pasta is perfectly tender. Allow the mixture to cool slightly, then gradually add the cheddar cheese, 1/4 cup at a time, tossing until fully incorporated to avoid clumping.
Serve immediately and enjoy!
Notes
Note 1: For the most possible flavor, make your own taco seasoning (otherwise we recommend a good brand for the most flavor).
1 teaspoon each paprika, cumin, garlic powder, onion powder
1/2 teaspoon oregano
(Use these seasonings in place of the taco seasoning packet.)Note 2: Various brands of enchilada sauce can vary quite a bit in heat. I like Old El Paso mild red enchilada sauce in this recipe.Note 3: Liquid is depending on 12 ounces regular spaghetti being used. Use a food scale (if possible) to be precise here!Note 4: If you are using a packet, they're typically a lot more salty, so adjust salt/pepper to taste.Note 5: Troubleshooting:
Sauce soaked up and pasta not tender? Lower the heat slightly. Add extra broth if needed.
Sauce not soaking in? Increase the heat.
Storage: Taco Spaghetti is best enjoyed right off the stove! However, you can keep it in the fridge for up to 3 days or freeze for up to 3 months. To reheat, heat it on the stove and add a splash of broth or water to return sauciness.