Preheat your oven to 350°F.
Cut the spaghetti squash in half lengthwise and remove the seeds. Drizzle the inside of the squash with olive oil and season with salt and black pepper.
Place the squash halves cut-side down on a baking sheet and bake for 45 minutes to 1 hour, or until the flesh is tender and easily shredded with a fork.
While the squash is baking, heat a large pan over medium heat and cook the ground beef until browned.
Add the diced white onion and minced garlic to the pan. Cook until the onion is softened.
Season the beef mixture with salt, black pepper, and Italian seasoning to taste. Pour in the jar of vodka sauce, stir to combine, and let the sauce simmer on low for about 1 hour.
Once the spaghetti squash is done, use a fork to scrape the flesh into strands and transfer the strands to a casserole dish.
Pour the simmered meat sauce over the spaghetti squash and mix well until the squash strands are coated.
Preheat the oven to 400°F. Top the mixture with shredded mozzarella cheese and bake for about 10 minutes, or until the cheese is melted and bubbly.
Remove from the oven and let it cool slightly before serving.
