Sprinkle the yeast and sugar over the water in a measuring cup. Stir until the yeast dissolves.
In a large mixing bowl, combine the flour and salt. Add the yeast mixture and stir until well blended. Cover with plastic wrap. Let rise in a warm place for 1-1/2 hours.
Pour about 2 inches of oil into a deep heavy saucepan or deep fryer. Heat the oil until the temperature reaches 375 degrees or until a drop of the dough slipped into the oil sizzles and turns brown in 1 minute.
Drop the dough by tablespoons into the hot oil. Do not crowd the pan. Cook the zeppole until golden brown and puffed, aout 2 minutes. Remove the zeppole with a slotted spoon and drain them briefly on paper towels. Repeat with the remaining dough.
Put the zeppole in a paper bag, add the confectioners sugar, and shake them until well coated. Serve immediately.