Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan and set aside.
In a medium bowl, whisk together the flour, baking soda, baking powder, cinnamon, and salt. Set aside.
In a large mixing bowl, cream together the softened butter and granulated sugar until light and fluffy.
Beat in the eggs one at a time, then stir in the vanilla extract and yogurt (or sour cream) until well combined.
Gradually add the dry ingredients to the wet ingredients, mixing until just combined. Do not overmix.
Fold in the diced apples and nuts (if using) until evenly distributed.
Pour the batter into the prepared loaf pan. In a small bowl, mix together the brown sugar and cinnamon, then sprinkle it evenly over the top of the batter.
Bake for 55-65 minutes, or until a toothpick inserted into the center comes out clean.
Allow the bread to cool in the pan for 10 minutes before transferring it to a wire rack to cool completely.