Dice the large onion into small pieces and mince the 5 garlic cloves. Break the 8 oz pasta into roughly 1-inch pieces and set aside. Shred the parmesan cheese fresh if not already done—this ensures it melts smoothly into the soup rather than clumping. Have all ingredients measured and ready before you begin cooking.

Melt the 1.5 tbsp butter in a large pot over medium heat. Once melted and foaming, add the diced onion and a generous pinch of salt, cooking for 5-7 minutes until the onion softens and turns translucent. I like to let the onions caramelize just slightly for a deeper flavor foundation. Stir in the minced garlic and cook for 1 minute until fragrant.

Increase the heat to medium-high and add the 1 lb ground beef to the pot with the aromatics. Break the meat apart with a spoon as it cooks, stirring occasionally for 5-7 minutes until it's fully browned and no pink remains. Drain excess fat if needed. Stir in the 1.5 tbsp Italian seasoning and cook for 30 seconds to toast the spices and release their oils into the meat.

Pour in the 64 oz beef broth and 15 oz diced tomatoes (with their juice) and bring to a boil. Once boiling, add the broken pasta pieces and stir well to prevent sticking. Reduce heat to a gentle boil and cook for 8-10 minutes, stirring occasionally, until the pasta is tender but not mushy. The soup will thicken slightly as the pasta releases its starch.

Reduce the heat to low and add the 0.75 lb baby spinach to the pot, stirring gently for about 1 minute until the spinach wilts completely. Remove the pot from direct heat and stir in the freshly shredded parmesan cheese until melted and incorporated. I find that adding the cheese off the heat prevents it from becoming grainy or clumping. Taste the soup and season with salt and pepper to your preference, remembering that the beef broth and parmesan already contribute saltiness.