Cut medium-size watermelon into 1 cubes (rind removed) until you have roughly 2 lbs. fruit. Transfer to laarge glass jar, pour in one 750 ml. bottle good-quality tequila, seal jar, and allow to steep for 2 days.
To make 2 margaritas:.
Combine 4 oz. of watermelon-infused tequila, 2 cups crushed ice, 2 oz. frozen limeade, 2 pieces of infused watermelon from jar, and 1 1/2 oz Cointreau in blender. Puree until slushy. Garnish with small wedge of watermelon.