Preheat the oven to 350˚F. Lightly spray a loaf pan and set aside.
In a large bowl, cream together the butter and sugars until light and fluffy. Mix in the eggs one at a time until fully incorporated. Add in the yogurt, banana and vanilla, and mix until fully combined.
In a separate bowl, mix together the flour, baking powder, baking soda and cinnamon. Slowly add in the dry ingredients to the wet ingredients until just combined.
Fold in the apples and walnuts. Pour the batter into the prepared pan and bake in the preheated oven for 1 hour, or until a toothpick inserted in the center comes out clean.