Preheat the oven to 200 degrees C and soak the oats in the milk. Butter a deep baking dish.
Fill the apples with jam and sprinkle with rum.
Cream the butter and sugar together. Beat in the salt, egg yolks, cottage cheese, lemon zest and lemon juice. Mix until creamy, then stir in the oats, milk and bicarb soda.
Beat the eggwhites to soft peaks and lightly fold in.
Pour batter into the baking dish and push in the whole apples. Bake 35-45 minutes until batter is cooked.