Heat a large skillet over medium heat. Add 1 pound ground beef and 1 medium onion (diced). Cook, breaking the beef into pieces, until the beef is no longer pink and the onion is softened, about 5–7 minutes.
Carefully drain and discard any grease from the skillet.
Return the skillet to medium heat and add 1 (28-ounce) can crushed tomatoes, 1 cup water, 1 teaspoon Italian seasonings, and 2 1/2 teaspoons Dijon mustard. Stir to combine and bring the mixture to a boil.
Stir in 2 cups pasta, cover the skillet, and reduce the heat to a simmer. Season with salt and pepper to taste. Cook for 25 minutes, stirring occasionally, until the pasta is al dente and most of the liquid is absorbed.
Remove the lid and stir in 1 cup shredded sharp cheddar cheese until melted and evenly distributed.
Stir in 1 cup diced dill pickle until combined. Taste and adjust salt and pepper if needed.
Serve the skillet hot.