Step 1

Preheat a fan-forced oven to 180C / 350F. Spray an 8x8” square cake tin with oil spray and line with baking paper.

Step 2

Add the all-purpose flour, corn starch, powdered sugar, salt, and lemon zest to the bowl of a food processor. Blitz until well combined, about 30 seconds. Add the butter and blitz for about 30-40 seconds until you reach pea sized butter.

Step 3

Pour into the cake tin and spread out. Press down firmly using our hands or a flat-bottomed glass/measuring cup. Bake for 12 minutes or until light and golden. Allow to cool slightly.

Step 4

Lower your oven temperature to 160C / 320F. Add the lemon zest, caster sugar and flour to a large mixing bowl. Use a whisk to combine. Then add the eggs and lemon juice. Whisk until just combined. Take care not to overmix.

Step 5

Pour into the slightly cooled shortbread base and bake for 22-25 minutes or until the middle is set and only has a slight jiggle in the very center. Take care not to overbake or it will feel like eating rubber and won’t be perfectly gooey. Allow to cool at room temperature and then chill in the fridge to set for 2 hours before slicing.