In the bowl of a stand mixer, combine the flour with the butter, baking powder, sugar and lemon zest, and mix. The mixture will have a sandy texture.
Add the eggs and continue mixing. If the dough is too sticky, add a little flour.
Roll ⅔ of the dough in a pie pan and place in the refrigerator.
Cut the quince (or guava) paste into small pieces and pour into a saucepan over low heat with 2 tablespoons of sugar and 2 tablespoons of water. Stir constantly over low heat, until it melts and becomes a thick jam. Remove from heat and let cool.
Remove the pie pan from the refrigerator and fill it with the jam, pouring it evenly.
Roll out the rest of the dough to a thickness of ⅛ inch (2 mm) and cut into strips about ½ inch wide (1 cm).
Cover the pie with the strips of dough, making a lattice pattern.
(Optional) Glue the edges carefully, by applying another strip of dough all around the pie.
Sprinkle shredded coconut around the edges of the pie after brushing with melted butter.
Bake in a hot oven until the dough is golden brown, about 30 to 40 minutes.