1. Prepare the Crust

1. Preheat your oven to 350°F (175°C).
2. Line a 9×13-inch baking pan with parchment paper, leaving overhang for easy removal.
3. In a mixing bowl, cream together softened butter and powdered sugar until smooth.
4. Add flour and salt, mixing until a soft dough forms.
5. Press the dough evenly into the bottom of the prepared pan.
6. Bake for 20–22 minutes, or until lightly golden around the edges.
7. Remove from the oven and set aside.

2. Make the Lemon Filling

1. In a large bowl, whisk together granulated sugar and flour.
2. Add eggs one at a time, whisking well after each addition.
3. Stir in lemon juice, lemon zest, and vanilla extract (if using).
4. Pour the filling over the hot crust immediately after removing it from the oven.

3. Bake Again

1. Return the pan to the oven and bake for 22–25 minutes, or until the center is just set and slightly jiggly.
2. The filling will firm up as it cools.
3. Remove from the oven and allow to cool to room temperature.

4. Chill and Slice

1. Once cooled, refrigerate for at least 2 hours to fully set.
2. Use parchment overhang to lift bars out of the pan.
3. Slice into 16 squares or rectangles using a sharp knife, wiping between cuts for clean edges.

5. Garnish and Serve

1. Dust bars generously with powdered sugar just before serving.
2. Garnish with lemon zest or fresh berries for an extra touch.