- Preheat oven to 180°C (350°F).
- Grease a 2 L (8 in.) square baking pan and line with two rectangles of parchment paper. Paper should hang over edges of pan to create “handles.” Set aside.
- Blend flour, nuts, icing sugar, cornstarch, and salt in a food processor until smooth.
- Add cubes of butter and pulse until mixture resembles coarse crumbs.
- Press evenly into baking pan and bake on middle rack for 25 minutes until golden brown. Remove from oven.
- Reduce oven temperature to 160°C (325°F).
- Lightly whisk eggs, sugar, lemon juice, flour, vanilla extract, and salt in a bowl.
- Carefully pour custard over warm crust.
- Bake for about 25 minutes until custard is just set.
- Let cool to room temperature, then refrigerate for at least 4 hours.
- Removal from pan
- Lift out of pan using parchment paper handles.
- Dust with icing sugar and cut into 16 squares.
Baking until “just set” means the corners of the cake should be firm and the centre still jiggles slightly when you shake the pan.