Peel and cut the squash into approximately 1.27-2.5cm (½-1 inch) cubes. Spray the bottom of your air fryer basket with cooking spray and add the prepared squash. Air fry for 10 minutes at 180°C (35°F).
After the 10 minutes is up, remove the basket and shake the squash. Lightly brush with olive oil and sprinkle with salt. Cook for another 10 minutes.
Meanwhile, melt the butter in a small saucepan. Add the sage leaves and cook for 3-4 minutes, stirring constantly. Make sure not to overcook the sage leaves, or the butter might become bitter.
Transfer the prepared squash to serving plates. Pour the prepared butter over the squash and garnish with sage leaves. Sprinkle with black pepper.
Finely grate the parmesan cheese. Sprinkle the squash with shredded parmesan. Taste and optionally add more salt. Serve immediately.