Preheat oven to 425°F.
Line two baking sheets with a layer of the heavy gauge aluminum.
Bring a large pot of water to a boil.
Use a sharp knife to cut the root tip off each Cipollini onion. Add the onions to the boiling water and allow to boil for 2 to 3 minutes.
Handle each cooled onion by its stem. Squeeze the papery peel, pushing up against the onion as you work.