Cook spaghetti by boiling a large pot of salted water over high heat. Once boiling, add spaghetti and cook until al dente, about 8-10 minutes. Drain and set aside.

In a large skillet, heat a drizzle of olive oil over medium heat. Add the ground beef and diced onion, cooking until browned and translucent, about 5-7 minutes. Add minced garlic and sauté for 1 more minute.

Pour in the tomato sauce and add Italian seasoning. Let the sauce simmer for 5-10 minutes, until bubbling gently.

In a bowl, mix the cooked spaghetti with softened cream cheese and sour cream until well-coated.

Preheat oven to 350°F (175°C). In a greased baking dish, layer half of the creamy spaghetti mixture, half of the meat sauce, and a generous layer of shredded cheddar cheese. Repeat with remaining ingredients.

Cover with aluminum foil and bake for 25 minutes. Remove foil and bake for an additional 10-15 minutes, until the cheese is bubbly and golden.

Let the casserole rest for about 5 minutes before serving. Slice into squares and enjoy.