Preheat your oven to 350°F (175°C). Line an 8-inch square baking pan with parchment paper. In a mixing bowl, combine 1 cup of all-purpose flour, 1/4 cup of powdered sugar, and a pinch of salt. Cut in 1/2 cup of cold unsalted butter until the mixture resembles coarse crumbs. Press the mixture into the bottom of the prepared pan and bake for about 18-20 minutes, or until lightly golden brown.

In a clean mixing bowl, whisk together 1 cup of granulated sugar and 2 large eggs until light and frothy, about 2 minutes. Add in 1/4 cup of freshly squeezed lemon juice and the zest from one lemon. Gently fold in 1/4 cup of all-purpose flour until just combined.

Pour the lemon filling over the pre-baked crust. Spread it evenly and bake for another 20-25 minutes until the edges are set but slightly jiggly in the center.