This tart is if a linzer cookie and a frangipane tart met, fell in love and had a baby. I was actually doubting it during the process and you might too but have faith it turns out fabulous. You have to dollop the frangipane dough on top of the jam and spread it without incorporating it with the jam. It takes a little patience and love but if you take your time the reward is delicious. —singing_baker
Make the dough. Pulse the hazelnut flour, all purpose flour, brown sugar, salt and cinnamon in a food processor. Pulse in butter one tablespoon at a time. With machine running add egg. If dough is not yet sticking together add water a little bit at a time until dough just comes together. Flatten into a disc, wrap in plastic and put in fridge until firm.
Roll out dough to fit a 4x14 rectangular tart pan. Fit into tart pan. Pull away scraps. Prick bottom of tart all over with a fork and put into freezer until firm. Preheat oven to 350 degrees. Line tart pan with parchment and fill with pie weights. cook for 12 minutes. Take out pie weights and parchment and cook for 10 minutes longer. Set aside to cool.
Make filling: In a bowl of a stand mixer beat butter, sugar and almond paste until fluffy. Add Almond extract and salt. Then add eggs one at a time until all incorporated, scraping down sides of bowl as needed. Add almond flour and all-purpose flour until all incorporated.
Spread Jam on bottom of tart. Dollop spoonfuls of batter on top and spread evenly trying not to incorporate it with the jam. Sprinkle sliced almonds on top. Bake tart for 30 minutes until puffed and golden enjoy!