In a saucepan whisk together lemon juice, lemon zest, egg yolks, granulated sugar, and salt. Stir constantly over medium-low heat for 20–25 minutes until thick and glossy.

Remove from heat and whisk in the cubed cold butter until smooth, then cool completely.

In a small bowl whisk together all-purpose flour, baking powder, and sea salt.

In a large bowl, rub granulated sugar with lemon zest until aromatic. Add softened butter and cream until fluffy and pale.

Beat in egg and vanilla until glossy.

Fold the dry ingredients into the wet mixture until just combined.

Scoop dough into 1–1.5 inch balls. Press each center gently with a 1/2 tsp to make a shallow well.

Chill the tray for 1 hour.

Preheat the oven to 350°F (175°C). Bake cookies for 8–9 minutes until edges are set and centers still soft. Cool on the sheet for a few minutes, then transfer to a rack.

Lightly dust cookies with powdered sugar and spoon or pipe cooled lemon curd into the wells.