Follow these steps to bring this delightful beverage to life:

1. Start by blending the watermelon cubes in a blender until smooth. This process only takes about a minute but ensures you capture all the sweet juices.
2. Pour the blended watermelon through a fine-mesh sieve into a large pitcher to remove any pulp, leaving you with a smooth juice.
3. Add the freshly squeezed lemon juice and sugar to the pitcher. Stir until the sugar is completely dissolved. I find this part meditative, reminiscent of watching my mother stir her famous lemonade, always tasting to adjust the sweetness just right.
4. Add the cold water to the pitcher and mix well. If you prefer your lemonade with a bit of fizz, this is where you can substitute in sparkling water.
5. Refrigerate the lemonade for at least an hour before serving to let the flavors meld together. Patience is key, as it reminds me of the anticipation I felt as a child waiting for the lemonade to chill on a hot summer day.
6. Serve over ice and garnish with fresh mint leaves for a refreshing finish.