Cut off the upper part of the apple including the core with a sharp knife and carefully core the apple. The typical baked apple shape should be created.
Lightly caramelize the sugar in a pot, add the butter and let it foam up briefly. Deglaze with the apple juice. Add the rosemary sprigs and cook until the sugar has dissolved. Pour the caramel sauce into an ovenproof dish.
Cream the butter with the egg, mix in the remaining ingredients and fill the apples with the mixture.
Carefully place each apple in the caramel sauce and bake at 170 °C for about 35 minutes.
Remove the hot apples from the oven and arrange them in a deep dish together with the sauce.