Most margarita recipes involve curocao, triple sec or grand marnier. All are LOADED with sugar. Here's a great recipe that is pretty much 0g carbs!
First, a little bit of background. Curocao is a traditional Caribbean alcohol made with orange peels, grapefruit peels, rum, and a LOT of sugar. From that base are created other 'blends' such as triple sec and cointreau. Grand Marnier is in essence a French version made with orange peels, sugar and brandy.
1/2 tsp orange extract
1 packet Splenda (or 2 tsp powdered)
1 tsp water
1 shot tequila
1/8 tsp lime juice
1/4 tsp lemon juice
Mix together the orange extract, Splenda and water. This pretty much is the curocao - orange extract is up to 85% alcohol. Put crushed ice into a shaker and pour this liquid over the ice. Now add in 1 shot tequila, plus the lemon and lime juice. Shake thoroughly and pour into a glass.
You are practically at 0g of carbs here. You get a tiny amount of carbs (let's say 0.4g) from those dashes of lemon and lime juice.
Lisa Shea's Library of Low Carb Books