Sift together flour, sugar, baking powder and salt.
Rub in the butter until crumbly. Add the egg, yolk and vanilla, and form the dough.
Preheat oven to at 180°C/350°F. Grease and flour a 24cm/10-inch tart pan. Line the base and sides with ¾ of the dough.
Mash the quince jam with the boiling water and fill the crust.
Roll out the rest of the dough, cut it into strips and weave a lattice top over the jam. Bake for 30-35 minutes and then let it cool.