Step 1: Brown the ground beef in a large skillet or Dutch oven over medium-high heat. Break it up with a spoon as it cooks until no pink remains.
Step 2: Drain any excess grease from the browned meat.
Step 3: Add the chopped onion and bell pepper to the skillet. Sauté for 5-7 minutes, until the vegetables soften.
Step 4: Stir in the minced garlic and cook for another minute until fragrant.
Step 5: Pour in the crushed tomatoes, diced tomatoes (undrained), tomato sauce, beef broth, and taco seasoning. Stir well to combine.
Step 6: Bring the sauce to a simmer, then reduce the heat to low, cover, and let it cook for 15-20 minutes, allowing the flavors to meld.
Step 7: While the sauce simmers, cook the spaghetti according to package directions in a separate large pot of salted boiling water until al dente. Drain well.
Step 8: Stir the drained spaghetti directly into the simmering taco meat sauce. Toss until the pasta is evenly coated.
Step 9: Remove from heat and stir in 1 cup of the shredded cheddar cheese, allowing it to melt into the hot pasta and sauce.
Step 10: Serve immediately, topped with the remaining 1 cup of shredded cheese and your favorite taco toppings.