Prepare the rim: On a small plate, spread salt or sugar. Rub the rim of your glass with a lime wedge, then dip the rim into the salt or sugar mixture. Set glasses aside.
Combine ingredients: In a cocktail shaker filled with ice, add the tequila, orange liqueur, lime juice, cranberry juice, pomegranate juice, and simple syrup.
Shake well: Close the shaker and shake vigorously until the outside is very cold, about 15 seconds.
Strain and serve: Fill your prepared glass with fresh ice. Strain the margarita mixture into the glass.
Garnish: Add a few fresh cranberries, pomegranate arils, or a rosemary sprig to the drink before serving.
For a pitcher: Multiply all liquid ingredients by the number of servings desired. Mix all ingredients (except ice) in a pitcher. Chill for at least 2 hours. When ready to serve, pour over ice and garnish individual glasses.
Notes
For a mocktail version, substitute the tequila and orange liqueur with 3 oz of sparkling water or non-alcoholic spirit alternative.
Adjust simple syrup based on the sweetness of your cranberry and pomegranate juices.
For a deeper red color, use less lime juice or add a splash of grenadine.