Squeeze the lemon. Wash apples, grate them dry and cut off a lid each time. Remove the core e.g. with an apple corer. Remove the flesh with a small knife so that a narrow edge remains.
Drizzle apples with lemon juice.
Finely chop the flesh. Mix with muesli, almonds and jam and fill into the hollowed apples.
Place apples in an ovenproof dish and bake in a preheated oven (electric oven: 200 °C/ convection oven: 175 °C/gas: level 3) for approx. 15 minutes. Place the apple lids on the apples after half the cooking time.
Mix yoghurt, milk and honey. Stir in sauce powder and whisk until creamy for about 1 minute. Arrange baked apples with the sauce and serve warm.