Adjust oven racks to top and bottom positions and heat oven to 500 degrees. Arrange potatoes2 pounds on rimmed baking sheet, pour ¾ cup water into baking sheet, and wrap tightly with aluminum foil. Cook on bottom rack until paring knife or skewer slips in and out of potatoes easily (poke through foil to test), 25 to 30 minutes. Remove foil and cool 10 minutes. If any water remains on baking sheet, blot dry with paper towel.