for the crust
1 1/4 cups all-purpose flour
1/4cup granulated sugar
3 tablespoons confectioners’ sugar, plus more for sprinkling
1 teaspoon finely grated lemon zest
1/2 teaspoon very finely chopped fresh rosemary
1/4 teaspoon fine sea salt
10 tablespoons unsalted butter
For the curd
4 to 6 meyer lemons (3/4 cup juice, 1 tablespoon zest)
1 1/2 cups sugar
2 large eggs plus 3 yolks
1 1/2 teaspoons cornstarch
Pinch of fine sea salt
4 tablespoons cold butter, cut into cubes
1/4 cup extra-virgin olive oil
Flaky sea salt, for sprinkling
Heat oven to 325F and line foil sling for your 9×9 inch baking pan. Spray with baking spray and set aside.
To make the shortbread base, pulse together the flour, granulated sugar, confectioners’ sugar, lemon zest, rosemary and salt in a food processor. Add butter and pulse to cut the butter into the flour until a crumbly dough forms. Press dough into prepared pan and bake until shortbread is pale golden all over, 30 to 35 minutes.
While the shortbread is baking, prepare the lemon curd: Grate a tablespoon zest from lemons and set aside. Squeeze lemons to yield 3/4 cup juice.
In a small saucepan, whisk together lemon juice, sugar, eggs and yolks, cornstarch and fine sea salt over medium heat until boiling and thickened, 2 to 5 minutes. Make sure mixture comes to a boil or the cornstarch won’t activate. Remove from heat and strain into a bowl. Whisk in butter, olive oil and lemon zest.
When the shortbread is ready, take it out of the oven and carefully pour the lemon curd onto the shortbread base; return the pan to the oven. Bake until topping is just set, 10 to 15 minutes more. Allow to cool to room temperature, then refrigerate until cold before cutting into bars (use the sling to pull them out of the pan and then cut on a cutting board). Sprinkle with confectioners’ sugar and flaky sea salt right before serving.