Preheat oven to 180c/350f
Shift the flour and add the baking powder.
Beat butter and sugar until fluffy. Add one egg at a time to the batter.
Slowly start to add the combined flour and baking powder. Beat on low for a few seconds. Remove the bowl from the mixer and transfer to a second bowl. Fold in the Greek yogurt, the cubed apples, and cinnamon powder.
Use a spatula to combine the ingredients.
Fold the batter into a medium size round cake pan.
Use the extra butter to coat the cake pan until it's completely coated. Then add extra flour to the pan and use your hand to help the flour cover the surfaces around and on the bottom of the pan. Fold out the excess flour
Fold and spread the batter evenly in the baking pan.
Bake until golden brown. Use a cake tester to see if the cake is ready. Let the cake cool on a wire rack.
Transfer the cake to a serving platter, sprinkle it with powdered sugar, and serve.