Peel and finely chop the sweet potatoes.
Steam the sweet potatoes and mash them smoothly.
Mix the mashed sweet potatoes with plain yogurt, egg, sugar, and salt thoroughly.
Sift cake flour and baking powder, then add to the mixture and combine well.
Shape the dough into rounds and line a pan with parchment paper.
Bake in a preheated oven at 180°C for 20-25 minutes.