1. Preheat oven to 350F. Lightly grease a 9×5 loaf pan then line with parchment paper.

2. In the bowl of a large food processor, add the flour, sugar, and salt. 3. Add the cold butter and pulse until butter is finely cut into the flour and a dough forms, about 1-2 minutes. Resist adding any liquid. It’ll seem really powdery then eventually turn into a dough.

3. Alternatively you can add the ingredients to a bowl and use a pastry blender to make the dough.

4. Transfer the mixture to the loaf pan and pat evenly into the bottom. 6. Bake for 20-25 minutes or until golden brown on the edges.

5. Meanwhile, make the filling: In a large bowl, whisk together the egg, egg yolk, and both sugars until sugar dissolves and mixture looks pale yellow. Try not to whisk too much air into it. Whisk in the flour and baking powder then the lemon zest and juice.

6. Once the crust has finished baking, turn the temperature down to 325F. Give the filling one last whisk (it’ll be runny) then immediately pour over the hot crust and put back in the oven. Bake for 20-25 minutes or until set and golden brown (it may slightly wiggle but top should be solid when touched).

7. Cool in the pan for 30 minutes then carefully remove and transfer to a wire rack. Cool until room temperature.

8. Dust with powdered sugar then refrigerate for at least 2 hours. Cut into squares.

Store in an airtight container and refrigerate for up to 1 week.