Most likely it has not baked for long enough. When in doubt, bake for another five minutes. When it comes to cakes, you can check it is cooked by inserting a skewer in the middle of the cake. If it comes out clean, the cake is baked. With this particular recipe, the apple sauce can make the cake seem like it's fully cooked when it isn’t yet. Remember, the cake should look golden brown and feel firm when you insert the skewer. If in doubt bake, for another five minutes.