3 ounces fresh squeezed blood orange juice
1 ounce fresh lime juice (reserve one wedge for the glass)
1 part Cointreau
2 parts tequila
blood orange slices to garnish (optional)
black rimming salt or sugar (optional, plain rimming salt will do as well)
Spread a small mound of sugar or salt on a small plate. Moisten the outer rim of a margarita or martini glass with a lime wedge, then dip the rim into the salt/sugar to lightly coat. Set aside.
In a cocktail shaker filled with ice, combine orange juice, lime juice, Cointreau and tequila. Shake to combine. Strain into a glass (add more ice, or crushed ice, if you like). Garnish with a blood orange slice and serve immediately.