In a shaker, add tequila (reposado or añejo), fresh lime juice and Cointreau.
Fill the shaker with ice and shake well for 10–15 seconds until properly chilled.
Taste and adjust if needed—more lime for bite, a small pinch of salt if it needs lifting.
Run a lime wedge around the rim of your glass, scatter sea salt onto a small plate and run rim of glass along salt. Fill the glass with ice and set aside.
Strain over the prepared glass. Garnish with a lime wedge and serve immediately.