In a large skillet, brown the ground beef over medium-high heat. Break it up into crumbles as it cooks.
Sprinkle the taco seasoning mix over the browned beef. Stir well to coat the meat evenly with the seasoning.
Add the drained diced tomatoes to the skillet with the seasoned beef. Stir and cook for a few minutes until heated through.
In a large bowl, combine the shredded cheddar and Monterey Jack cheeses.
Add the sour cream to the bowl of shredded cheeses. This will make your mac and cheese incredibly creamy.
Add the cooked macaroni to the bowl with the cheeses and sour cream. Also, pour in the beef and tomato mixture
Pour in the salsa and mix it into the mac and cheese. This adds a delightful Tex-Mex twist.