For the almond shortbread crust:

1. Preheat the oven to 350 degrees F. Line a 9x5 loaf pan with parchment paper, leaving the ends hanging over the sides for easy removal. 
2. In a medium bowl, combine the all-purpose flour, almond flour, powdered sugar, and salt.
3. Cut the cubes of butter into the flour mixture with your fingers or a pastry cutter until the butter is pea-size. Lastly, mix in the almond extract. 
4. Transfer the dough to the prepared loaf pan and pack it down with the back of a rubber spatula into an even layer. 
5. Dock the dough with the tines of a fork, then bake for 14-16 minutes or until the edges are barely golden and the center no longer looks doughy.

For the lemon filling:

1. While the crust bakes, make the lemon filling. In a medium bowl, add the sugar and lemon zest. Rub them together with your fingers until the it resembles wet sand and the zest smells aromatic.
2. Stir in the cornstarch and salt. Then, add in the lemon juice and eggs. Whisk vigorously for 2-3 minutes until the eggs are fully incorporated into the mixture. 
3. Once the crust is done baking, immediately pour the lemon filling over the hot crust.
4. Reduce the oven temperature to 325 degrees F and bake for 15-16 minutes or until it is completely set in the middle.
5. Allow the bars to cool completely at room temperature. Then, cover with plastic wrap chill in the fridge for at least one hour or overnight.
6. Just before serving, dust with powdered sugar and enjoy!