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

In a separate bowl, whisk together the egg, milk, melted butter, and vanilla extract until smooth.

Carefully pour the wet mixture into the dry ingredients, mixing gently until just combined.

Fold in diced apple into the batter until evenly distributed.

Let the batter rest for about 5 to 10 minutes at room temperature.

Preheat a lightly greased griddle or non-stick frying pan over medium heat.

Using a ¼ cup measuring cup, pour the batter onto the hot griddle.

Cook until bubbly and edges are firm, about 2-3 minutes, then flip and cook the other side.

Transfer finished pancakes to a warm oven set at 200°F until ready to serve.