1. Preheat oven to 350 degrees F. Line an 8×8 baking dish with foil.
2. Melt the butter in a heavy-bottomed sauce pan over medium heat, whisking occasionally. When the butter starts to foam, whisk constantly until it turns brown and fragrant. Remove immediately to a large mixing bowl. Allow the butter to cool, then whisk in 2 tablespoons lemon juice.
3. Add the flour, sugar, and salt to the butter and beat with a mixer on low speed until just combined. Don’t overmix. Press into the bottom of prepared pan.
4. Bake at 350 for 30 minutes until the edges just start to turn golden. The middle will still VERY gooey, but the cake is definitely done at this point. Allow to cool completely.

Lemon Glaze

1. Meanwhile, make the lemon glaze. Melt 1 tablespoon of butter and whisk into powdered sugar. Add the zest of 1 lemon, and just enough lemon juice to make a thick, but pourable glaze, about 1½ – 2 tablespoons. Whisk until smooth and combined.
2. Pour glaze over shortbread and allow to set before cutting into bars.