Bring a large pot of salted water to a boil. Add the spaghetti squash and cover the squash with a small plate to keep it submerged. Cook for 12 minutes, until tender. Drain and let the squash sit cut side down in a strainer to cool slightly. Using a fork, scrape the squash into strands.
In a large skillet, melt the butter. Add the pancetta and cook over high heat, stirring frequently, until browned and crisp, about 6 minutes. Add the garlic and crushed red pepper and cook until fragrant, about 30 seconds. Add the squash, season with salt and cook until dry, about 5 minutes. Stir in the cheese and sunflower seeds, transfer to a bowl and serve right away.
The recipe can be prepared through Step 1 and refrigerated overnight.