Place potatoes in a microwave safe bowl. Cover bowl tightly with plastic wrap. Polk 3 or 4 holes in the top for ventillation. Microwave on high for 6 to 7 minutes. When you remove the potatoes from the microwave, use oven mitts. The steam that comes off the food can burn your hands. The potatoes may stick together. Separate them as best you can. They tend to come a part while cooking in the oven.

Mix mayonaise with dill and garlic powder in a medium size bowl. Add the potatoes and stir to coat well with the mixture.

Spray an oven safe baking dish with non stick spray. Add the potatoes and the onions. Salt and pepper to taste. Cook at 425 degrees for 20 to 25 minutes or until potatoes turn brown and crispy, turning potatoes once half way through cooking. When potatoes are done, remove from the oven and sprinkle with Parmesan cheese. Toss and serve.