Place the sugar and the butter I a food processor and pulse a few times until just combined.
Add the egg and pulse for a few seconds. Add the flour and pulse for a few seconds. STOP as soon as the dough comes together.
Add 1 tbsp of ice cold water if the dough seems dry. Over processing will result in a tough dough.
Knead lightly on a floured surface. Shape into a flat disc, cover in cling and let it rest in the fridge for a minimum of 30min.
Roll the pasty dough to a thickness of about 3mm. Line a 23-25cm pie dish with a removable base (4cm deep).
Leave a bit of overhanging pastry above the edge (as pastry dough shrinks after baking). Chill for 30min.
Preheat oven to 190C
Re-roll the extra pastry dough into a rough rectangular shape and place on baking paper on a baking sheet. Cut 1cm long strips and chill.
Blind bake the pastry: Carefully line the pastry dough with foil paper. Fill it with dried or ceramic beans. Bake for 15-20min until firm and the edges are golden.
Carefully remove from the oven, remove the foil and beans, and return to the oven for 5-8min until the whole tart shell looks dry and a light beige color.
Take the tart out, place on a rack to cool a bit and reduce the oven to 150C.
Prepare the filling: Beat the butter and sugar with a handheld mixer (or in a stand alone) until light in color and fluffy.
Gradually add the eggs and the vanilla, whisking well. Gently fold in the flours.
Using a very sharp knife, gently trim the excess (overhanging) pastry. Spread the jam inside the baked tart shell.
Fill it with the almond mixture. Use the strips of dough to create a lattice design on top of the tart, leaving about 2cm gaps in between the strips.
Cut and tuck in the excess pastry that sticks out.
Bake for 30-35min until golden brown.
Take out of oven and while still warm, use a brush to gently paint the top with the apricot jam glaze. Wait for the tart to cool before serving.