1 oz Cointreau (triple sec works just fine)
3/4 oz fresh squeezed lime juice - one half of a juicy lime is the right amount when squeezed with the help of a fork - otherwise use a whole lime if it is drier
2 oz tequila (if this sounds scary, try 1.5 oz first)
Juice of half an orange
Combine ingredients in a shaker. Add ice and shake it like a Polaroid picture - it will be a bit frothy. Poor contents of shaker into glass including ice. Salted rim optional.
Enjoy!
