Make the shortbread crust:

1. Combine flour, powdered sugar, salt, butter and lemon zest in the large bowl of an electric mixer and beat with the paddle attachment until the mixture is coarse and crumbly.
2. Press the dough together with your hands and turn it out into a parchment-paper-lined 13 x 9″ baking pan.
3. Bake at 325F for about 20 minutes, or until lightly golden. Place aside to let cool slightly.

Make the lemon bars:

1. Preheat the oven to 325 (F).
2. Whisk granulated sugar, eggs, lemon juice, lemon zest in a medium bowl until well-mixed.
3. Pour over slightly cooled shortbread crust and return to 325F oven. It will be very runny!
4. Bake for 20 minutes, or until the edges are golden and the topping has set. Let cool on a baking rack completely, then cover and refrigerate overnight.
5. Combine the powdered sugar, ground cinnamon and ground ginger in a small bowl.
6. To serve, slice the chilled bars into small squares or long rectangles. Dust the bars with the powdered sugar-spice mixture. Let sit at room temp for 20-30 minutes before serving.