In a large mixing bowl, combine all-purpose flour, baking powder, ground cinnamon, ground nutmeg, salt, and granulated sugar. Whisk together until well blended.

In a separate bowl, whisk together the large egg, milk, melted unsalted butter, and vanilla extract until fully combined.

Pour the wet mixture into the bowl with the dry ingredients. Gently fold until just combined; some small lumps are fine. Let the batter rest for five minutes.

Peel and dice the medium apple into small pieces, then fold the diced apples into the pancake batter.

Heat a lightly greased griddle or non-stick skillet over medium heat. Ensure it's hot enough; droplets of water should skitter and evaporate.

For each pancake, pour 1/4 cup of batter onto the cooking surface. Cook for about 2-3 minutes until bubbles form on the surface.

Carefully flip each pancake and cook for an additional 2-3 minutes until golden brown.

If making a large batch, transfer the cooked pancakes to an oven set at 200°F to keep warm until all are cooked.