To add a salt rim to margarita glasses, pour salt onto a small plate. Then rub the lime wedge around the rim of each glass. Dip glasses into the salt and twist. Set them aside.
Place the sliced plums into a small saucepan with water and sugar. Bring to a boil and reduce to simmer for 5-7 minutes or until the fruit is soft and the water has turned the shade of the plums.
Allow the mixture to cool for 10 minutes before pouring it into a blender with the lime juice, lime zest, orange juice, and Tequila. Blend until smooth.
Strain into prepared glasses filled with ice. Garnish with a slice of plum. Cheers!