This recipe comes from one of my favourite cookbooks by Marcella Hazen Essentials of Classic Italian Cooking. It's super easy and delicious.
3 apples of any firm, but not sour, cooking apples
1/4 granulated sugar
2 tablespoons of rum
the peel of one lemon grated
2/3 cup flour
Peel and core the apples and cut them in slices of 3/8 inch thick.
Put the sugar, rum and grated lemon peel in a bowl together with the apple slices. Let steep for 1 hour.
Use the flour an 1 cup of water to make a batter.
Pour enough oil into a skillet to come to 1/2 inch up the sides, and turn on the heat to high.
Take the apple slices out of the bowl and pat them dry with paper towels. When the oil is very hot, dip them in the batter and then slip as many of them into the skillet as will fit loosely. Fry them to a golden brown on one side then turn them and do the other side. Transfer them to a cooling rack to drain. Repeat the procedure until all the remaining slices are done. Sprinkle with the icing sugar and serve while hot.