To make the watermelon puree, combine some ripe watermelon in a blender or food processor and puree completely.

Strain the watermelon puree to get a clean watermelon juice.

To make the blackberry ice, add a few blackberries to each section of a jumbo ice tray.

Add water to fill the cavities of the ice tray.

Freeze until completely frozen.

To prep the glasses, run lime along the perimeter of the glass.

On a small plate, sprinkle a little of the tajin.

Turn the glass upside down and turn in a circular motion in the tajin to basically create a salt rim with the tajin.

In a cocktail shaker, combine the watermelon juice, orange liqueur, lime juice and crushed ice.

Shake vigorously.

Add 1 blackberry cube into each glass and pour the Watermelon Margarita mixture over it.

To serve, garnish with lime wedges and watermelon pieces.

Add jalapeño slices if using.