1. Preheat your oven to 350 F (175 C). Grease and flour a 9×5-inch loaf pan, or line it with parchment paper, leaving an overhang on the long sides to easily lift the bread out later.

2. In a large bowl, combine the all-purpose flour, granulated sugar, baking powder, baking soda, salt, ground cinnamon, and ground nutmeg. Whisk these dry ingredients together until they are well combined and there are no lumps.

3. In a separate medium bowl, whisk together the egg, milk, vegetable oil, and vanilla extract until smooth. Pour the wet ingredients into the dry ingredients and mix with a spatula until just combined. Be careful not to overmix; a few small lumps are perfectly fine.

4. Gently fold the finely diced apples into the batter. Ensure the apple pieces are evenly distributed throughout the mixture.

5. In a small bowl, combine the 1/2 cup all-purpose flour, light brown sugar, granulated sugar, and 1/2 teaspoon ground cinnamon. Pour in the melted butter and mix with a fork until crumbly. Stir in the chopped pecans.

6. Pour the bread batter into your prepared loaf pan, spreading it evenly. Sprinkle the pecan streusel topping generously over the entire surface of the batter. Place the loaf pan in the preheated oven and bake for 45-50 minutes, or until a wooden skewer or toothpick inserted into the center of the bread comes out clean.

7. Once baked, remove the bread from the oven and let it cool in the pan for about 10-15 minutes before carefully lifting it out onto a wire rack to cool completely. If desired, whisk together the powdered sugar, milk or water, and vanilla extract for the glaze. Drizzle the glaze over the cooled bread just before serving.