Sift all the dry ingredients together into a bowl. Make a well in the centre and add the orange zest, egg, pumpkin puree and milk, then beat to a stiff batter.
Melt the butter and fry the apple slices until golden and just softened. Keep hot.
Heat a large frying pan over a moderate heat then brush it with melted butter and pour 2 to 3 tablespoons the pancake batter into the pan, spreading it lightly. Cook 2 to 3 pancakes at one time. Cook for 1 to 2 minutes or until bubbles appear at the edges. Carefully turn over the pancakes and cook for a further 1 to 2 minutes, or until golden brown and firm to the touch.