Cook the spaghetti in a large pot of boiling salted water according to package directions until al dente. Drain and set aside.
Heat the olive oil in a large skillet over medium heat. Add the diced onion and cook, stirring occasionally, until tender and translucent, about 5–6 minutes.
Add the minced garlic to the skillet and cook for 30–60 seconds until fragrant.
Add the ground beef and increase heat to medium-high. Cook, breaking up the meat, until no longer pink, about 5–7 minutes. Drain excess fat if desired.
Reduce heat to medium and stir in the taco seasoning, Rotel tomatoes (undrained), tomato paste, beef broth, and softened cream cheese. Stir until the cream cheese melts and the sauce is smooth, about 4–5 minutes.
Add the cooked spaghetti to the skillet and toss to combine. Sprinkle the shredded Colby Jack cheese over the pasta and stir until the cheese is fully melted and the sauce coats the noodles.
Garnish with chopped fresh cilantro and serve immediately.
