Step 1: In a large, deep skillet or Dutch oven, brown the ground beef (or preferred protein) over medium-high heat. Break it up with a spoon as it cooks. Once no pink remains, drain any excess fat.
Step 2: Add the chopped onion and bell pepper to the skillet with the cooked beef. Sauté for 5-7 minutes, until the vegetables are softened and fragrant. Stir occasionally.
Step 3: Sprinkle the taco seasoning and minced garlic over the beef and vegetables. Cook for 1 minute, stirring constantly, to toast the spices and release their aromas.
Step 4: Pour in the diced tomatoes (undrained), tomato sauce, beef broth, and water. Stir well to combine, scraping up any browned bits from the bottom of the pan. Bring the mixture to a gentle simmer.
Step 5: Carefully add the uncooked spaghetti to the simmering liquid. If using long spaghetti, break it in half. Ensure the pasta is mostly submerged. You may need to press it down gently with tongs or a spoon. Bring the liquid back to a simmer.
Step 6: Reduce the heat to medium-low, cover the skillet, and cook for 12-15 minutes, or until the pasta is al dente and most of the liquid has been absorbed. Stir occasionally to prevent the pasta from sticking and to ensure even cooking.
Step 7: Remove the skillet from the heat. Stir in the shredded cheddar cheese until it's melted and creamy. For an extra creamy touch, you can also stir in a spoonful of sour cream or cream cheese at this stage.
Step 8: Garnish with fresh cilantro, green onions, and any of your favorite taco toppings. Serve immediately and enjoy your delicious one-pan taco spaghetti!