Preheat your oven to 350°F (175°C) and position a rack in the middle. Grease and flour a 9x5-inch loaf pan, or line with parchment paper with overhanging edges for easy removal.
In a medium bowl, whisk together the flour, baking soda, salt, cinnamon, and nutmeg until well combined.
In a large bowl, beat the butter and sugar together until light and fluffy, about 3-4 minutes.
Beat in the eggs one at a time, then stir in the vanilla extract and milk.
Gradually fold the dry ingredients into the wet mixture, stirring just until combined. Do not overmix.
Gently fold in the diced apple, pear, and nuts (if using) until evenly distributed throughout the batter.
If using the streusel topping, combine brown sugar, flour, and cinnamon in a small bowl. Cut in the cold butter using a pastry cutter or your fingertips until the mixture resembles coarse crumbs. Stir in nuts if desired.
Pour the batter into the prepared loaf pan, spreading it evenly. If using streusel, sprinkle it over the top.
Bake for 55-60 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. If the top browns too quickly, loosely cover with aluminum foil after 40 minutes of baking.
Allow the bread to cool in the pan for at least 15 minutes before removing and slicing.