First get started on the pastry. Sieve the flour, salt and baking powder into a bowl then rub in the butter until the mixture resembles breadcrumbs.
Add the chilled water a small amount at a time and mix with a knife until you have a good dough. Roll into a ball, cover in cling film and chill in the fridge while you make the filling.
Cream together the butter and sugar then beat in the egg. Fold in the sieved flour and baking powder until you have a smooth cake batter.
Roll out the pastry until around 5mm thick. Using a 3 inch cutter, cut rounds and press gently into a bun tin. Place a small amount of jam on top of the pastry then top with 1 tsp of the cake batter. Using the scraps place a cross of pastry on top of the batter.
Bake at 200oc for 10 min, or until well risen and golden.