Pour enough oil into an electric skillet so that the bottom is well covered, about 1/8" deep. Depending on how fast you are, either turn the skillet on now or wait until you start on the apples. The oil should be at 375 degrees.
Combine in a bowl the beaten egg, milk, sugar, cinnamon and sour cream. In separate bowl, whisk together flour, baking powder and salt. Add flour mixture to egg mixture and mix well.
Peel apples, core and slice them into 1/4" slices. Dip slices in batter and carefully place in oil. Cook for 1 to 2 minutes. Turn and cook 1 to 2 minutes more. Remove fritters and drain. Sprinkle with powdered sugar if desired. Serve warm.