Preheat and prepare the squash:
Preheat the oven to 400°F. Slice the spaghetti squash in half lengthwise and scoop out the seeds. Place both halves on a baking sheet and drizzle with olive oil, coating the inside and outside. Lightly season with salt and pepper. Lay the squash cut-side down and use a fork to pierce several small holes in the outer skin.

Roast the squash:
Roast for 45 minutes, or until the flesh is tender and easily separates into strands with a fork.

Make the meat sauce:
While the squash is roasting, heat 2 tablespoons of olive oil in a large pan over medium-high heat. Add the onions and sauté until tender and fragrant, about 3–4 minutes. Stir in the garlic, then add the ground beef, breaking it apart with the back of your spoon as it cooks. Season with salt, pepper, and smoked paprika.

Simmer the sauce:
Once the beef is fully browned, drain any excess grease if needed. Pour in the marinara sauce, then season with oregano, basil, and a pinch of sugar (optional). Adjust seasoning with more salt and pepper to taste. Reduce the heat and let the sauce simmer until the squash is ready.

Assemble and broil:
When the squash is done, remove it from the oven and carefully flip the halves over. Use a fork to gently pull the strands toward the center. Spoon the meat sauce over each half, then top with shredded mozzarella cheese.

Broil and serve:
Return the squash to the oven and broil for 5–7 minutes, until the cheese is melted and bubbly. Top with fresh basil and serve warm.