In a small mixing bowl whisk together flour, sugar, baking powder, and salt. Set aside.
In a separate bowl whisk together milk and egg; add vanilla and whisk until well combined.
Whisk milk mixture into flour mixture; set aside.
Slice apples and cut out the middle part of the apple slices. I use a small round cookie cutter to pop them out.
In a large skillet, heat the oil over medium-low heat to 375˚F degrees.
Dip the apple rings in the batter then transfer them to the skillet and cook in batches, 1 to 2 minutes per slice, or until golden, turning once to cook the other side.
In a bowl or plate combine sugar and cinnamon; mix well.
Sprinkle cinnamon sugar over the apple rings while still hot.