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 add a lemon slice as garnish.
Notes
Use a vodka you like as the flavor comes from it.
Use freshly squeezed lemon juice. Bottled lemon juice just isn't as good.
You can replace the lemon juice with lime juice if you prefer.
Do a dry shake first before adding the ice which cools the drink but strengthens the foam.