Add ground beef to a large pot or Dutch oven over medium-high heat. Let it cook undisturbed for 5-6 minutes to develop browning on the bottom.
Add the chopped onion and break the beef into small pieces with a wooden spoon. Cook for another 5 minutes until the onion softens and the beef is completely cooked through. If using regular ground beef, spoon out excess fat, leaving about 1 tablespoon.
Stir in the minced garlic, red pepper flakes, Italian seasoning, and dry orzo. Cook for 1 minute, stirring constantly.
Pour in the tomato sauce, beef broth, heavy cream, and Worcestershire sauce. Stir to combine and bring to a gentle bubble.
Once bubbling, reduce heat to medium or medium-low to maintain a gentle simmer. Cook uncovered for 10 minutes, stirring frequently to prevent sticking, until the orzo is tender and the sauce has thickened. The mixture should gently bubble rather than boil vigorously.
Remove the pot from heat completely. Stir in the grated Parmesan cheese and fresh spinach until the spinach begins to wilt.
Cover the pot and let it rest for 3-5 minutes to allow the orzo to absorb remaining liquid and the sauce to thicken to your desired consistency.
Remove the lid, stir well, and season with salt and black pepper to taste. Serve immediately while hot.
