Preheat the oven to 400°F. Line a rimmed baking sheet with high-heat-resistant parchment paper.
Prepare the squash:
Pierce the squash in a few spots with a sharp knife. Place it on a microwave-safe plate and microwave it for 5 minutes; turn to the other side and microwave it for 5 more minutes, until soft to the touch (careful, the plate and the squash will be hot).
Let it stand for 5 minutes to finish cooking and cool off a little. Using a sharp knife, cut the squash in half lengthwise. Allow it to cool for 5 minutes until easier to handle. Scoop out the pulp and seeds from the center, then rake a fork back and forth to remove strands of the flesh onto a serving bowl. Set aside.
Bake the meatballs:
Prepare the meatballs: In a medium bowl, combine the beef with salt, pepper, garlic powder, onion powder, smoked paprika, and oregano. Form the mixture into 24 small meatballs. Place the meatballs on the prepared baking sheet. Bake them until they are cooked through, for about 10 minutes.
Finish the dish:
Heat the marinara sauce in a large saucepan over medium-low heat. When the meatballs are ready, transfer them to the warm sauce and continue to simmer for 5 more minutes.
Pour the meatballs and sauce on the spaghetti squash strands, garnish with parsley and parmesan, and serve.
Video
Notes
It's best to mix the sauce into the squash strands at the very last minute, right before eating, to prevent the noodles from becoming soggy.
I like to use the microwave because it's fast and convenient. But as an alternative to using the microwave, you can bake the spaghetti squash in the oven instead.
You can keep the leftovers in the fridge, in a sealed container, for 3-4 days. While it's best to keep the squash separate from the sauce, if you already mixed them together, don't toss the leftovers! Soggy or not, they will still be delicious, gently reheated in the microwave at 50% power or in a 350°F oven.