Lemon and limoncello squares

Crust:

1. Position rack in centre of oven.
2. Preheat oven to 170°C (325°F).
3. Butter a 20-cm (8-inch) square baking pan and line with parchment paper, letting parchment paper overhang on each side.
4. In a bowl, mix flour and sugar, lemon zest and salt.
5. Mix in butter using your fingers, until the dough is a shortbread-like consistency.
6. Add egg to the mixture.
7. Lightly press the dough into the buttered, lined baking pan.
8. Cook for 20 minutes, or until crust is golden brown.

Lemon filling:

1. In a pot, mix all the ingredients, with the exception of the olive oil. Bring to a boil, while whisking.
2. Remove the pot from the element, and mix in olive oil while whisking.
3. For a smoother filling texture, strain the mixture through a sieve, then pour into crust.
4. Cook in the oven for 10 minutes at 170°C (325°F) or until the filling has set.
5. Let cool and refrigerate for roughly 2 hours. Remove from baking pan and cut into squares.
6. Dust with icing sugar and fleur de sel, to taste.