Preheat oven to 450 degrees (425 convection). Spray a large baking sheet with cooking spray.
In a large bowl mix together melted butter, garlic powder, onion powder, paprika, salt and pepper, along with half of the parmesan. Add the sliced potatoes to the bowl and with a rubber spatula toss the potatoes with the butter mixture until well coated.
Spread the potatoes in a single layer on the baking sheet, not touching. Sprinkle the rest of the grated parmesan on top of the potatoes. Bake for 20 - 25 minutes, until tender when pierced with a fork, browned and crispy. Remove from oven and sprinkle with parsley if using. Top with a sprinkle of salt if necessary.
Enjoy!