Combine the egg whites, sugar, cream of tartar, and kosher salt in the large bowl of a stand mixer. Set this bowl over a pan of barely simmering water, ensuring the bowl does not touch the water. Whisk constantly until the sugar has dissolved and the mixture is warmed through; the temperature should reach about 160°F (use an instant-read thermometer for accuracy).

Attach the bowl with the warm egg white mixture (from Step 1) to a stand mixer fitted with the whisk attachment. Beat the mixture on high speed until soft peaks form, which typically takes about 5 to 6 minutes. The peaks should gently bend over rather than stand upright.

Transfer the whipped meringue (from Step 2) into a piping bag fitted with a large star tip, or simply snip off 1/2 inch from the tip of the bag if you don’t have a tip. Twist the bag closed to push the meringue towards the opening. Reserve the bagged meringue at room temperature until you're ready to assemble the cocktails. I find that preparing the piping bag ahead of time makes for a much neater topping later!

Place two martini or coupe glasses in the freezer while you make the cocktails so they are nicely chilled and ready for serving.

In a cocktail shaker, combine vodka, limoncello, orange liqueur (such as Cointreau or triple sec), fresh lemon juice, and simple syrup. Fill the shaker with ice, cover, and shake vigorously until the outside is very frosty, about 20 seconds. I always make sure the shaker is extremely cold before straining to ensure a super refreshing cocktail!

Strain the shaken cocktail mixture into the chilled glasses, leaving just a little room at the top for the meringue. Using the prepared piping bag, pipe meringue (from Step 3) in a circular motion on top of each cocktail—trust it will float! Finally, use a kitchen torch to lightly toast the top of the meringue as a finishing touch.