PREHEAT THE OVEN TO 3507, and line a glass 9-5-3-inch loaf pan with parchment paper, leaving enough parchment overhang to form handles. If using a metal loaf pan, be sure to cover the entire surface so the metal doesn't react with the lemon during baking.

Place the butter in a medium-size bowl. Add the powdered sugar and 1 cup of the flour. Work the butter into the sugar and flour, using your fingertips or a pastry cutter. When the mixture comes together into crumbs that hold together when squeezed in your palm, you're done.

Pack this mixture firmly into the prepared loaf pan. Bake for 25 minutes.

While the crust bakes, in a large bowl, using an electric mixer on medium speed, beat together cup of the granulated sugar and the lemon zest, lemon juice, and eggs for 1 minute, until foamy. Add the baking powder and remaining 1 tablespoon of flour and continue to beat until no lumps of flour remain.

Pour the lemon filling over the parbaked crust. Bake for another 20 to 23 minutes. The filling should set entirely and not have any jiggle to it

Let the lemon bars cool entirely in the pan, and then lift them out, using the parchment paper as handles.

Refrigerate for at least 4 hours before serving, for best flavor. Before serving, sprinkle the remaining 2 tablespoons of granulated sugar on top, and caramelize with a culinary torch. Slice in half, and then serve immediately (the sugar crust will soften as it sits).