Add brown sugar, salt and melted butter to the plain flour and mix well until fine crumbs form.
Pour the mixture into a 20x20 cm (8x8 inch) baking pan lined with parchment paper.
Use the bottom of a glass to press the mixture down evenly into a flat layer.
Bake the crust in the preheated oven at 190°C (374°F) for about 15 minutes, or until lightly golden brown.
Once the crust is baked, remove the tin from the oven and let cool slightly.
How to Prepare the Lemon Topping:
In a mixing bowl, add lemon zest, sugar and flour and whisk well to combine.
Squeeze fresh lemon juice. Set aside.
In another mixing bowl, add eggs and lemon juice, and whisk until well combined.
Sieve the egg mixture into a bowl with the sugar, flour and zest. Whisk to combine and smooth.
Pour the lemon topping mixture over the warm crust.
Return the pan to the oven and bake at 170°C (338°F) for 15 minutes, or until the lemon topping is set and no longer jiggles when gently shaken.
Remove from the oven and allow to cool completely in the pan on a wire rack before chilling in the refrigerator for two hours.
Once cooled, dust the top of the lemon dessert squares with icing sugar.
Cut into squares, serve, and enjoy these lemon dessert squares!
Notes
Properly Measure Ingredients: Use a kitchen scale or measuring cups/spoons to measure your ingredients accurately. Don't overmix the crust: Mix the ingredients until they are combined when making the shortbread crust. Overmixing can result in a tough crust. Evenly Press the Crust: Press the shortbread crust evenly into the bottom of the pan using the bottom of a glass. An even crust ensures uniform baking and a consistent texture. Use a Microplane for Zesting: Use a microplane grater or zester to zest the lemons. This tool creates fine zest without any bitter white pith, resulting in a more intense lemon flavor. Bake Until Set: Bake the lemon squares until the top is set and no longer jiggles when gently shaken. Keep an eye on them towards the end of the baking time to avoid overbaking, which can result in a dry texture.