Preheat oven to 350 degrees.  Spray a 9 x 5-inch loaf pan with nonstick spray.

CRUMB TOPPING

1. Add all the ingredients to a small bowl and mix together with a spoon or your hands.  The mixture should be just moist enough to slightly stick together.  Set aside while you mix the batter.

BATTER

1. In a medium bowl, whisk together the flour, baking soda, salt, sugar, and cinnamon and set aside.
2. In a large bowl, add the melted butter, buttermilk, sour cream, eggs, and vanilla and mix well by hand or with an electric mixer.  Add the dry ingredients and mix until the dry ingredients are just incorporated.  Do not overmix.  Fold in the apples.
3. Transfer the batter to the loaf pan, using an offset spatula to evenly spread the mixture.
4. Sprinkle the crumb topping over the batter.  Using a knife, swirl it through the topping and the batter in a figure-eight motion, then use your hand or a spatula and gently press the topping into the batter.
5. Bake the bread for 50 minutes and check the bread by inserting a toothpick into the center for doneness.  The toothpick should come out almost clean, with moist crumbs on it.  If it’s still doughy continue baking and test every 5 minutes until done.  Ovens vary, but it should not take longer than 70 minutes.  If the bread begins to brown too much on top before it’s done in the middle, place a foil tent over it.  Allow bread to rest for 5 minutes.  Run a sharp knife around the edges and invert the bread onto a wire cooling rack to cool.
6. Slice bread and serve warm with butter or at room temperature.
7. Wrap the leftover bread tightly in plastic wrap.  Bread will stay fresh for up to 4 days.
8. Bread can be frozen for up to 3 months.  Wrap the bread securely in 3 layers of plastic wrap and freeze.