Prepare a round cake mould (22 cm) by covering the bottom with parchment paper and greasing the sides. Pre-heat the oven to 180 degrees.
Batter: In a large bowl, mix together yoghurt, eggs, sugar, vanilla extract and oil. Then add baking powder and salt, and gradually add flour while whisking the dough. Keep whisking the dough for 2-3 minutes until it reaches a silky texture. Set aside
Apples: Peel and core the apples, and cut each apple in 8 wedges. Place the apple wedges on top of the caramel layer all around.
Caramel sauce: For the caramel sauce, add all ingredients to a sauce pan. Let it sit on the stove for 4-5 minutes on low heat; it will make itself. Immediately pour it into the mould as it hardens quickly. Place apples in circular form on top and pour batter on top.
Bake the cake for 35-40 minutes, and test with a toothpick whether it's done. Cover with foil if the cake gets too brown and the cake isn't done.When done, let the cake cool for 10 mins, then flip it over to have the caramelised apples on top. Serve as is, or with a scoop of ice cream