01 -
Preheat the oven to 180°C (350°F). Line two baking sheets with parchment paper.
02 -
In a medium bowl, rub the sugar and lemon zest together until well combined and fragrant.
03 -
In the bowl of an electric mixer fitted with the paddle attachment, cream the butter and lemon-sugar together until light and fluffy, about 5 minutes.
04 -
Add the egg and beat until well combined, then scrape the sides of the bowl thoroughly. Add the lemon juice, vanilla and lemon oil (if using), and beat until fully incorporated.
05 -
Add the flour, baking powder and salt, and mix until uniformly combined without overmixing.
06 -
Scoop the dough into mounds (approximately 2 tablespoons each) on the prepared baking sheets, leaving about 5cm of space between them to allow for spreading. Stagger the rows for even baking.
07 -
Bake the cookies until they just begin to brown at the edges, 16 to 18 minutes, rotating the baking sheets halfway through. Cool completely on the baking sheets.
08 -
Fill a medium saucepan with 5cm of water and bring it to a simmer over medium-low heat. Set a medium bowl over the pot, add the egg whites, cream of tartar, sugar, salt and vanilla (if using), and whisk to combine. Heat, whisking constantly, until the mixture reaches 71°C (160°F) on a thermometer.
09 -
Remove the bowl from the heat and continue to whisk until the meringue reaches stiff peaks, or transfer the heated mixture to the bowl of a stand mixer fitted with the whip attachment and whip on medium-high speed until stiff peaks form, about 3 minutes.
10 -
Scoop a tablespoon of meringue onto each cookie and use a small spatula to spread it across the surface. Use a kitchen torch to lightly toast the meringue until golden. Serve within 8 hours for best texture and flavor.