Sift the flour, salt and baking powder into a mixing bowl and stir in the sugar.
Make a well in the centre and add the egg yolk.
Mix it in, alternately adding a little milk and melted butter.
Then stir in the vanilla essence.
In a separate bowl beat the egg whites until stiff but not dry, and fold lightly into the mixture, together with the chopped pineapple.
Heat the waffle iron and pour a little batter on to it.
Cook on both sides for a total of 2-3 minutes.
Transfer to a warm serving dish to keep hot while making the rest of the waffles.
Serve as soon as possible with hot pineapple syrup.