Method

• 1.
  Grease and line base of a 4cm-deep, 30cm x 20cm slice pan.
• 2.
  Place the butter and icing sugar in a food processor and process until well combined. Add 2 cups (300g) of the flour and process until the mixture comes together in a ball. Press into the base of the prepared pan and chill for 15 minutes.
• 3.
  Preheat the oven to 170°C.
• 4.
  Place pan in the oven and bake for 15 minutes, then set aside to cool while you prepare the topping. Finely grate rind from 2 of the lemons, then juice all 4 (you will need about 90ml of juice).

• 5.
  Whisk together eggs and caster sugar in a large bowl until well combined. Add remaining flour, and the baking powder, rind and juice. Whisk gently to combine. Pour mixture over cooled base and return to oven for a further 30 minutes or until topping is set and tinged golden. Cool in the pan, then cut into slices.
• 6.
  Dust with extra icing sugar to serve.