Begin by combining brown sugar and grated lemon zest in a bowl. Cream with butter until light and fluffy, about 3-4 minutes.

Mix in one large egg and vanilla extract until smooth.

In a separate bowl, whisk together all-purpose flour, baking powder, and salt. Gradually add the flour mixture to the wet ingredients.

Cover the dough and chill in the refrigerator for 30 minutes.

Preheat oven to 350°F (175°C). Line two baking sheets with parchment paper.

Scoop tablespoons of chilled cookie dough onto prepared baking sheets. Bake for 10–12 minutes.

For the lemon curd, combine sugar, lemon juice, lemon zest, and egg yolks in a saucepan over medium heat. Stir until thickened.

Strain the lemon curd and mix in butter until melted. Chill.

For the meringue, place egg whites and sugar in a heatproof bowl over simmering water. Stir until mixture reaches 170°F.

Whip egg whites on high speed until stiff peaks form.

Dollop lemon curd onto cookies and pipe meringue on top. Toast lightly with a kitchen torch.

Serve at room temperature, storing leftovers in an airtight container.