Cut the apple into cubes. Mix the raisins, apple pieces, rum and lemon juice and let steep for 15 minutes.
Mix the flour, oatmeal, baking powder and cinnamon in a bowl.
Beat the butter and cane sugar in another bowl for about 2 minutes until creamy. Add the egg and vanilla sugar and mix well again.
First stir in half the flour mixture, then the apple-raisin-rum mixture and then the rest of the flour mixture.
Place the dough with a teaspoon on a baking sheet lined with baking paper and bake at 160 degrees for about 15-20 minutes. I usually use 2 teaspoons of dough for 1 cookie.