Step 1: Prepare the watermelon puree. In a blender, combine the cubed fresh watermelon. Blend until completely smooth. If you prefer a pulp-free margarita, strain the puree through a fine-mesh sieve into a bowl, pressing gently to extract all liquid. Discard any solids. You should have about 1.5 to 2 cups of watermelon juice for this watermelon margarita recipe.
Step 2: Rim your glasses (optional). If desired, moisten the rims of two margarita glasses with a lime wedge. Dip the rims into a shallow plate of coarse salt or sugar.
Step 3: Combine ingredients in a shaker. In a cocktail shaker, combine the watermelon puree (or strained juice), blanco tequila, fresh lime juice, and agave nectar (or simple syrup). The amount of sweetener can be adjusted based on the sweetness of your watermelon and your personal preference for this watermelon margarita recipe.
Step 4: Add ice and shake. Fill the cocktail shaker about two-thirds full with ice cubes. Secure the lid and shake vigorously for 15-20 seconds until the mixture is well-chilled.
Step 5: Serve your watermelon margarita recipe. Fill the prepared margarita glasses with fresh ice. Strain the contents of the shaker into each glass.
Step 6: Garnish and enjoy. Garnish each watermelon margarita recipe with a fresh lime wedge and a small watermelon triangle. Serve immediately and savor the taste of summer!