Preheat a fan-forced oven to 160°C (320°F) or conventional oven to 180°C (350°F).
Combine 150g almond flour, 30g erythritol, and salt in a bowl; incorporate melted butter and one egg until a cohesive dough forms.
Press the dough evenly into the base and sides of a 20cm (8-inch) loose-bottomed tart tin.
Blind bake the crust for 12 minutes until slightly firm and pale gold; remove and allow to cool for 5 minutes.
In a separate bowl, cream softened butter and 50g erythritol until aerated and light in color.
Gradually beat in two eggs and almond extract into the creamed butter, then fold in 100g almond flour until a smooth frangipane paste is achieved.
Spread the sugar-free raspberry jam in a uniform layer over the par-baked pastry base.
Spoon the frangipane mixture over the jam, smoothing the surface with a spatula to seal the edges.
Scatter flaked almonds evenly across the top of the frangipane layer.
Bake for 35-38 minutes until the frangipane is set in the center and the surface is golden brown.
Allow the tart to cool completely in the tin to ensure the almond structure sets before slicing.