Preheat oven to 425 F. Cut potatoes into 1/8 inch round slices. Arrange in single layer on greased baking sheet.
In a small bowl, combine melted butter, salt, pepper, paprika, cumin and onion. Evenly brush mixture over tops of potatoes (You may need spoon onion bits over potatoes).
Bake 15-20 minutes until potatoes are tender and golden brown. Remove from oven and turn oven to medium broil. Evenly sprinkle potatoes with parmesan cheese and broil (6-8 inches from heat) until cheese is melted and potatoes are crispy, about 3 minutes. Watch carefully to prevent burning.