Prepare the prickly pear juice: Using gloves, carefully peel the skin off the pear. Chop the inside and blend until smooth. Strain up to three times and set aside.
Make the margaritas: In a cocktail shaker, combine tequila, prickly pear juice, lime juice, and simple syrup. Add ice to chill. Dip chilled glasses in remaining lime juice and coarse salt and pour prepared margarita mix and serve.