Preheat oven to 180 °C hot air. Place the baking cups in the muffin tray.
For the muffins, wash, peel, halve, core and dice the apples. Sprinkle with lemon juice.
Sift the flour with baking powder and baking soda. Beat the egg, add sugar, vanilla sugar, oil, yogurt and apple cubes with the egg to the flour mixture.
Pour the batter into the ramekins and smooth it out.
Bake in the oven (top/bottom heat on the middle rack) for about 30 minutes.
Then let the apple muffins rest for about 5 minutes, remove and let cool.