3.5 cl (seven parts) tequila (100% agave, white)
2.0 cl (four parts) Cointreau or Triple Sec
1.5 cl (three parts) lime juice
Shake ingredients with ice and serve straight up.
Rub the rim of the glass with the lime slice to make salt stick to the rim.
Traditionally the drink was made with agave nectar instead of Triple Sec.
Update: I decided I don't like tequila much, so I won't be making these any more.