Heat the olive oil in a large skillet or deep sauté pan over medium-high heat. Add the ground beef and cook, breaking it up with a spoon, until browned and no longer pink, about 5 to 7 minutes. Drain off excess fat if needed.

Add the diced onion to the skillet and cook for 3 to 4 minutes, until softened. Stir in the garlic, Italian seasoning, salt, black pepper, and red pepper flakes if using, and cook for 30 seconds.

Stir in the tomato paste and cook for 1 minute to deepen the flavor. Add the diced tomatoes and beef broth, scraping up any browned bits from the bottom of the pan.

Bring the mixture to a boil, then stir in the orzo. Reduce the heat to medium-low and simmer, uncovered, stirring often, for 10 to 12 minutes, or until the orzo is tender and most of the liquid has been absorbed.

Stir in the heavy cream and Parmesan cheese until the sauce is smooth and creamy. Add the spinach and cook for 1 to 2 minutes, just until wilted.

Taste and adjust the seasoning with more salt and pepper if needed. Remove from the heat, garnish with parsley, and serve warm.