Preheat your oven to 350°F and lightly coat an 8½ x 4½-inch loaf pan with nonstick cooking spray. In a large bowl, whisk together the flour, granulated sugar, baking powder, and salt. In a separate mixing bowl, combine the milk, egg, melted butter, and vanilla extract, whisking until everything is fully blended. Pour the wet ingredients into the bowl of dry ingredients and gently stir until just incorporated, being careful not to overmix—the batter will be slightly runny. Transfer the batter to your prepared loaf pan, spreading it out evenly across the top. Bake the loaf for 60 to 70 minutes, or until the surface is golden brown and a toothpick inserted in the center comes out with a few moist crumbs. Once the bread is baked, take it out of the oven and allow it to cool in the pan for 10 minutes. Then, carefully lift the loaf from the pan and place it on a large piece of parchment paper. While the loaf is still warm, use a pastry brush to coat the surface with the melted butter for the topping. In a small bowl, combine the granulated sugar, cinnamon, and nutmeg, then sprinkle the mixture generously and evenly over the buttered loaf. Rotate the bread as needed to ensure all sides are thoroughly coated. Any extra topping mix can be saved for later use.