Dice 1 sweet potato and slice the remaining half thinly. Microwave for 3 minutes until cooked and set aside to cool.

In a bowl, cream softened butter using a whisk.

Add sugar and salt to the butter and whip until creamy.

Gradually add eggs in 5–6 portions, mixing well after each addition.

Sift cake flour and baking powder, then mix 1/3 of it into the batter.

Add half of the plain yogurt and mix, then incorporate the remaining dry ingredients.

Mix in the remaining yogurt and diced sweet potato until the batter is smooth.

Line muffin tins with parchment paper and fill each cup to 80% capacity. Top with a slice of sweet potato.