Spaghetti Squash with Hawaiian Meatballs start with juicy homemade meatballs that are smothered with a sweet and sticky, Polynesian pineapple sauce and served over baked spaghetti squash. Most of the ingredients may already be in your pantry.
Line a small rimmed baking sheet with parchment paper.
Pierce the squash in a few places with a fork and microwave it for 1 minute, to slightly soften.
Place the squash on a cutting board, and work very carefully. First slice off the stem end of the squash, then stand the squash upright on the flat end and carefully slice it in half from the top down to the cutting board.
Using a large metal spoon, remove the seeds and pulp from one half. (Store the other half wrapped tightly in plastic wrap in the fridge for up to 5 days.)
Lightly spray the cut side with non-stick cooking spray and sprinkle with salt and pepper.
Place the squash half, cut side down, in the baking sheet. Bake until fork-tender, about 45 minutes.
While the squash bakes, line another small rimmed baking sheet with parchment paper and set aside.
In a large bowl, combine ground beef, breadcrumbs, milk, egg yolk, 1/2 tablespoon soy sauce, Worcestershire, garlic powder, onion powder, and pepper. Gently mix ingredients until thoroughly combined but not packed down.
Divide the beef mixture into 8 equal portions and gently roll into balls which should measure between 1 1/2 and 2 inches across.
Arrange meatballs on prepared baking sheet, at least an inch apart.
Add to the oven and bake meatballs for 15 minutes or until golden brown and cooked through to the center.
While the meatballs and squash bake, dice the green pepper.
Then, in a saucepan set over medium heat, prepare sauce by combining pineapple, green pepper, ¼ cup water, soy sauce, honey, rice wine vinegar, brown sugar, and ginger.
Bring sauce to a boil, stirring occasionally. Boil about 5 minutes and then reduce to a simmer.
In a small bowl, use a fork to whisk together 1/2 tablespoon cornstarch and 1 1/2 teaspoons water.
Stream cornstarch mixture into simmering sauce while stirring. Allow sauce to cook for a few minutes until thickened and glossy, stirring occasionally. Turn heat to low and keep warm stirring occasionally.
Transfer the cooked spaghetti squash to a cutting board and allow it to cool about 10 minutes.
Remove the meatballs from the oven to a paper towel-lined plate to drain any grease. Cover to keep warm if needed.
Rake a fork back and forth across the squash to remove its flesh in strands. Transfer the strands to two serving bowls or plates.
Serve meatballs over the spaghetti squash with sauce poured on top. Garnish with fresh parsley if desired.