Preheat your oven to 375°F (190°C). Line a muffin tin with paper liners or lightly grease the tin.
Mix Dry Ingredients in a large bowl, whisk together the flour, granulated sugar, brown sugar, baking powder, cinnamon, nutmeg (if using), and salt until well combined.
Mix Wet Ingredients in a separate bowl, whisk together the eggs, melted butter, milk, and vanilla extract.
Combine Ingredients: Pour the wet ingredients into the dry ingredients and stir until just combined. Be careful not to overmix the batter.
Add Apples: Gently fold in the diced apples. If you’re using nuts or raisins, fold them in as well.
Spoon the batter into the prepared muffin tin, filling each cup about 3/4 full.
Bake for 18-22 minutes, or until a toothpick inserted into the center of a muffin comes out clean.
Allow the muffins to cool in the tin for about 5 minutes before transferring them to a wire rack to cool completely.