Place sugar, flour, baking powder and bicarbonate of soda in a food processor; blitz for 10 seconds to combine. Add butter, egg , egg yolk and vanilla extract; process until the mixture comes together in a ball, adding 1 tablespoon water or milk if needed.
Wrap pastry in cling film and chill for at least 30 minutes.
Combine quince jam and water in a saucepan; heat over low heat until smooth. Set aside to cool.
Preheat oven to 180 C / Gas 4. Lightly grease and flour a 23cm loose-based tart tin.
Roll out pastry to about 30cm and arrange in prepared tart tin; trim edges and re-roll remaining pastry into 10cm (2cm wide) strips to use for a lattice effect.
Spoon quince filling onto pastry case; lay 5 strips of dough parallel across pie, about 2cm apart, letting excess hang over rim. Arrange remaining strips diagonally across pie in opposite direction. Press ends firmly to rim of pie, trimming excess dough. Crimp edges with your fingers or a fork.
Bake in preheated oven for 30 minutes or until pastry is golden brown. Allow to cool in tin for 30 minutes before taking it out of the tin.