In a large mixing bowl, combine flour, sugar, baking soda, baking powder, salt and ginger and mix well. Add melted butter, vanilla, eggs and yogurt to this mixture and mix until there are no visible lumps of flour remaining, being sure to scrape the sides of the bowl as you mix. Divide this mixture evenly among the wells of the muffin pan, placing the batter over the apples. Bake for 30 minutes, or until cakes are golden brown, or when a toothpick inserted into the center of the cake comes out clean.