Cook pasta in a pot of boiling water as per package instructions, until al dente. Drain and set aside.
Meanwhile, in a large skillet, brown the ground beef along with the diced red bell pepper and onion, until beef is no longer pink. Drain any fat from pan and discard.
Add in the garlic, taco seasoning and salt and mix until combined. Add in the butter and melt into beef. Sprinkle the flour over the beef and stir, cooking an additional 1 to 2 minutes, until the flour is absorbed into the beef mixture.
Gradually add the beef broth to the pan, scraping any browned bits off the bottom of the pan. Bring mixture to a simmer and add in the tomato paste and stir until thickened.
Add in the sour cream and cheese to create a creamy, cheesy sauce. Add in the cooked pasta and stir to coat. Enjoy right away!
Notes
You can swap the tomato paste with 10oz. Rotel diced tomatoes. It will change the sauce to be a little thinner, but still delicious.