Preheat the oven to 400 degrees F. Line a rimmed baking sheet with high-heat-resistant parchment paper.
Prepare the spaghetti 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.
Prepare the meatballs: In a medium bowl, mix together 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, about 10 minutes.
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 top of the spaghetti squash strands, garnish with parsley and parmesan, and serve.
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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.