Bring a large pot of salted water to a boil and cook the 8 ounces of spaghetti according to package directions until al dente; drain and set aside.
In a large nonstick skillet over medium‑high heat, cook 1 pound ground beef, breaking it up, until no longer pink; drain any excess fat.
Sprinkle the 1‑ounce taco seasoning over the beef and add 2/3 cup water; stir and cook for 2 to 3 minutes until the seasoning is well incorporated.
Add 1 tablespoon tomato paste, the 10‑ounce can Rotel (undrained), the 10.75‑ounce can condensed cream of chicken soup, and the 8 ounces cubed Velveeta to the skillet; stir and cook over medium heat until the Velveeta melts and the mixture is smooth.
Stir in the shredded cheese until melted, then add the cooked spaghetti and the rinsed and drained 15‑ounce can black beans; toss gently to combine and heat through.
Sprinkle with 2 tablespoons chopped fresh cilantro, if using, and serve immediately.
