Preheat oven to 350 degrees. Grease 12 cup muffin tin. In a large bowl, combine flour, baking powder, cinnamon and salt. In a separate bowl, mix together the egg, sugar, applesauce, apple and oil. Combine the dry ingredients into the wet ingredients. Fold in the walnuts. Divide the batter into the greased muffin tin. Bake for 20 to 25 minutes.