In a skillet on medium-high heat, add the olive oil, ground beef, diced yellow onion, salt, and black pepper. Cook and brown the meat for 5-6 minutes or until no pink remains in the ground beef and the onions are translucent. Drain off all the excess fat from the skillet.

Transfer the cooked ground beef mixture to the insert of a 6-quart crockpot. Add the taco seasoning, Rotel diced tomatoes, 2 tablespoons of fresh chopped cilantro, spaghetti noodles, beef broth, and water. Give all the ingredients a stir, and be sure that all the spaghetti noodles are submerged in the liquid.

Place the lid on the crockpot and cook on HIGH for 2 hours (3½-4 hours on LOW). You can check for doneness at 1 ½ hours to be sure that you do not overcook your noodles.

Once the noodles are cooked, turn the crock pot off and remove the lid. Using a pair of tongs or a pasta spoon, give the spaghetti a stir to combine all the ingredients evenly. Add the shredded cheddar cheese to the spaghetti and stir again to combine. Top with the remaining 1 tablespoon chopped fresh cilantro and serve.