Preheat oven to 375°F.
Heat olive oil in a large skillet and sauté onion 2–3 minutes.
Add ground beef, garlic, salt, pepper, and Italian seasoning. Cook until browned; drain excess fat.
Add spinach to the skillet and cook 1–2 minutes until wilted.
In a saucepan, heat heavy cream and cream cheese until smooth.
Stir in mozzarella, Parmesan, and garlic powder until melted into a thick alfredo sauce.
Combine ground beef mixture with the alfredo sauce.
Transfer to a greased baking dish and top with mozzarella.
Bake 20–25 minutes until hot and bubbly.
Cool slightly and serve.