Tequila, triple sec and lime juice shaken with ice and poured into a glass with a salted rim. Three ingredients and three minutes, and the rim is done before anything else.
Lime, not lemon. The Spanish limón means lime in Mexico and in Colombia, and a margarita made with yellow lemon tastes flat and slightly soapy against the tequila. Squeeze it fresh: bottled lime juice has a cooked note that shows up immediately in a drink with only three ingredients. Do the rim first, before there is anything in the glass. Wet the outside edge with a cut lime and dip it into a saucer of salt, turning it. Salt on the inside of the glass falls into the drink and makes it briny, which is why the recipe says only the rim. Shake it hard and stop when the shaker is too cold to hold comfortably. That is both the chilling and the small amount of dilution the drink needs, and it happens in about fifteen seconds.