Grease the glasses and preheat the oven to 175 degrees.
Beat the butter with the sugar until frothy. Add calvados or apple juice. Mix the flour with baking powder and stir into the dough. Half fill the jars with batter.
Wash, peel and quarter the apples. Place 1 quarter each in the middle of the prepared glasses. Bake the cakes in the oven for about 30 minutes.
Take the glasses out of the oven. When the cakes have cooled, turn them out of the glasses or serve in the glass with a spoon to spoon. Dust with powdered sugar.