Blood orange sugar syrup
Bring the blood orange juice and sugar to the boil in a pan, boil until the sugar has melted, leave the syrup to cool.
Dip the rim of each glass in the blood orange juice, mix the sugar and grated lime zest, twist the rim in the sugar, chill.
Pour the blood orange syrup, reserved lime juice, liqueur, tequila and ice cubes into a shaker and shake well.
Pour the cocktail into the prepared glasses, serve immediately.