Preheat oven to 350°F. Grease or line loaf pan with parchment paper.
In a medium bowl, whisk together flour, baking powder, baking soda, salt, cinnamon, and brown sugar.
In another bowl, mix milk, oil, egg, vanilla, and cranberry sauce until smooth.
Stir in diced apples (and nuts if using).
Combine wet ingredients and dry ingredients just until blended. Don't overmix.
Pour the batter into the prepared pan.
In a small bowl, mix the streusel ingredients with a fork until crumbly, then sprinkle evenly over on top.
Bake for 55-60 minutes, or until a toothpick comes out clean.
Cool 10 minutes in the pan, then transfer to a wire rack to cool completely.