In a medium bowl, stir together flour, baking powder and salt. Set aside.
Using a stand or hand mixer, beat butter until fluffy and pale. Add egg yolks one at a time, then add sugar and beat until well combined. Slowly add flour mixture and mix until the dough just begins to come together. Form dough into a ball and cut in half. Wrap each half in plastic wrap and freeze for a minimum of 30 minutes.
Preheat oven to 350°F. Line an 8” x 8” pan with parchment paper on one side only, leaving a bit hanging over. Remove one piece of dough from the freezer and grate into the pan or on a large sheet of wax paper using the large holes of the grater. Pat the dough down gently and evenly. Mix together lemon zest with the apricot preserve, then spread over the dough. Grate the other piece of dough over the preserve. Pat down lightly, as you want to look crumbly. Bake for 40 minutes until golden in colour.
Remove from the oven and place on cooling rack. Sprinkle with confectioners’ sugar, some of it will soak in but that’s okay. Cool completely in pan and then cut into 9 equal squares. Dust a little more confectioners' sugar to serve if you so desire.
