A classic tequila cocktail which first appeared in print in Trader Vic’s 1946 Book of Food and Drink where it was called the "Mexican El Diablo".
Half-fill a cocktail shaker with ice.
Add the tequila, creme de cassis and lime juice; shake until well-chilled.
Strain into a glass over fresh ice.
Squeeze the juice from a lime wedge over the glass and drop the lime wedge in.