In a small bowl, combine the onion powder, garlic powder, smoked paprika, cayenne, salt and brown sugar.
In a large mixing bowl, toss squash with butter and olive oil. Add 1 tablespoon of the spice mixture to the bowl and toss well to coat.
Place squash on a sheet pan lined with parchment and bake for 40-45 minutes, tossing every 15 minutes, to allow for even browning. Sprinkle with 1 1/2 teaspoons more of spice mixture. Toss gently to coat and serve hot.