Cook the BeefIn a large skillet over medium-high heat, brown the ground beef until no longer pink. Drain any excess fat.
Season the MeatAdd the taco seasoning and water to the beef. Stir and simmer for 3–4 minutes until the sauce thickens slightly.
Add SalsaStir in the salsa and reduce the heat to low. Let the mixture simmer gently while you cook the pasta.
Boil the PastaIn a separate pot, cook the pasta shells according to package directions until al dente. Drain the pasta.
Combine and MeltAdd the cooked pasta to the skillet with the beef mixture. Sprinkle in the cheddar and mozzarella cheeses. Stir until the cheese melts and the pasta is coated in a creamy, cheesy taco sauce.
ServeSpoon into bowls and serve warm. Garnish with fresh herbs, extra cheese, or your favorite taco toppings if desired.