Heat a Dutch oven or large pot over medium-high heat and add the ground beef and chopped onion. Cook, breaking up the beef, until the meat is browned and the onion is softened, about 5–7 minutes.
Add the minced garlic and cook, stirring, for about 1 minute until fragrant.
Stir in the Rotel tomatoes, tomato sauce, taco seasoning, beef broth, tomato paste, and Worcestershire sauce. Bring the mixture to a boil.
Add the spaghetti noodles, reduce heat to medium so the mixture simmers, and cook uncovered, stirring frequently and scraping the bottom of the pot, until the pasta is tender, about 15–18 minutes.
When about 5 minutes of cooking remain, stir in the shredded cheddar and Monterey Jack cheeses until melted and evenly distributed.
Remove the pot from the heat, garnish with chopped cilantro if desired, and serve immediately.