Cream cheese is the real secret behind these lemon squares – they lend richness but also a tang that enhances the tart lemon. It also gives the lemon filling structure, so that it doesn’t leak into or underneath the shortbread base. Making them in a food processor also keeps the work time to a minimum, but they can also be easily mixed by hand.
Preheat the oven to 350 F. Grease and line a 9-inch (23 cm) square pan with parchment paper so that the paper comes up the sides.
To prepare the base, pulse the flour and sugar in a food processor to combine. Add the butter and pulse it until the mixture is an even crumbly texture, but the dough should not come together. Press this into the prepared pan.
3. Bake for 15 to 18 minutes until the base turns golden around the edges. Prepare the filling while the crust cools.
In a food processor, pulse the cream cheese with ½ cup of the sugar until smooth. Add the remaining 1 cup of sugar, the flour, lemon zest and baking powder and blend. Add the lemon juice and eggs and blend until smooth, scraping down the sides of the processor once or twice. Pour the filling over the cooled crust.
Bake for 35 to 40 minutes, until the edges are set and just show signs of soufflé-ing a little, but the centre should still have a bit of a jiggle to it. Cool the squares to room temperature before chilling for at least 3 hours before slicing.
The square can be kept refrigerated for up to 3 days.