Add all of the ingredients to a cocktail shaker without ice. Shake for 30 seconds. Add ice and shake for 30 seconds. Strain into a chilled coupe glass and top add a lemon peel as garnish.
Notes
Use a gin you like as some of the flavor comes from it.
You can leave the gin out if you like a lower alcohol content or want an even more prominent Aperol flavor.
Use freshly squeezed lemon juice. Bottled lemon juice just isn't as good.
You can replace the lemon with lime juice if you prefer.
Do a dry shake first before adding the ice which cools the drink but strengthens the foam.