Set aside one tablespoon of flour. Add the remaining flour into a a bowl of a food processor fitted with metal blade, followed by the baking powder, lemon zest and powdered sugar, and mix briefly with several pulses. Add cubed butter and pulse again.

Once you have a sandy mixture, add the yolk and pulse several times. Transfer onto a working surface, slowly incorporate the remaining tablespoon of flour if necessary, and knead briefly until the dough comes together.

Transfer the ball onto a sheet of cling film, flatten it into a disk and wrap it well. Let the dough rest in the refrigerator for 30 minutes to 1 hour.

Preheat oven to 170°C/340°F or with fan option on at 150°C/300°F. Arrange the baking tray onto the middle shelf.

Place the dough on a lightly floured surface and roll until the dough is approximately ⅛" thick. With a metal serving ring, cookie cutter or cup, cut circles about 2.5-inch/6cm in diameter.

Place half a teaspoon of jam in the center of each circle.

Bring the sides of the dough together as if to close the circle, and pinch the ends gently but firmly together to secure them.

Arrange the cookies on a baking sheet covered with parchment paper. Bake them for about 17 minutes or until golden on top. Remove them from the oven, then cool them on a baking rack.

Once completely cooled, sprinkle them with powdered sugar and serve them.