Squeeze the lemon to get the juice. Divide the juice into 2 small bowls. Peel, core, and then cut the apples into thin slices. One apple should be sliced thinly while the other is diced.
In a large bowl, combine the flour, baking powder, salt, and ground nutmeg. Add the chilled butter, then use a pastry blender to process/mix until the butter is fully broken up into small pieces.