Lightly grease 4-ounce aluminum tin and preheat oven to 350 degrees.
Sift flour, cocoa powder, baking powder, baking soda, nutmeg and salt into medium bowl.
In another medium bowl whisk together the butter, yogurt, vanilla, egg and sugars. Make a hole in the flour mixture and pour butter mixture into the hole. Using rubber spatula gently stir everything together until there are no more streaks of flour. Mixture will be thick
Fill 4-ounce aluminum tin evenly ¾ of the way
Bake for 8 to 10 minutes until cake springs back when touched.
Let cool completely on wire rack