Heat the olive oil in a large deep-sided pan (or large pot). Add the ground beef and cook until browned, breaking up the meat as it cooks. Drain any excess grease.
Add the taco seasoning, diced bell pepper, and Rotel tomatoes (with juices) to the pan. Stir to combine.
Add the water and spaghetti, spreading the spaghetti out slightly on the top so it’s somewhat submerged, and bring to a boil. Reduce the heat to medium-low, cover, and simmer until the pasta is al dente, about 15 minutes. Stir frequently.
Remove from heat. Stir in the sour cream and Mexican cheese until melted.
Top with tomatoes, jalapenos, and cilantro, if desired. Serve warm.
Notes
This recipe was only tested with spaghetti. So I cannot speak to the cook time of other pastas or if they will work.
Ground chicken or ground turkey can be substituted for the ground beef.
When reheating, you may need to add additional sour cream to loosen the sauce back up.