Preheat your oven to 350°F (175°C). Grease a 9x5-inch loaf pan.

In a medium bowl, whisk together the flour, baking powder, baking soda, salt, cinnamon, and nutmeg.

In a large bowl, beat the softened butter and granulated sugar until light and fluffy. Add the eggs one at a time, then stir in the vanilla extract.

Alternately add the dry ingredients and sour cream (or yogurt) to the butter mixture, mixing until just combined. Fold in the diced apples.

Pour the batter into the prepared loaf pan.

For the streusel topping, mix the flour, brown sugar, and cinnamon in a small bowl. Cut in the cold butter until the mixture resembles coarse crumbs. Sprinkle over the batter.

Bake for 50-60 minutes, or until a toothpick inserted into the center comes out clean.

If using the glaze, whisk together the powdered sugar, milk (or cream), and vanilla extract until smooth. Drizzle over the cooled bread.