Shake hard for about 15 seconds until the shaker feels very cold.
Strain into the prepared glass over fresh ice.
Garnish with a lime wedge (or a candy eye for extra spooky vibes) and serve.
Notes
Use silver/blanco tequila to keep the color bright. For a crowd, multiply ingredients and build in a pitcher, stirring with ice to chill. Add a splash of soda water for a lighter, bubbly version.