Blend Watermelon and Lemon in a high powered blender.

Strain juice in a fine mesh strainer.

Fill each glass about halfway with sparkling wine (you may need to do this just a little bit at a time to avoid overflow).

Carefully fill each glass with watermelon juice, leaving about an inch of room at the top.

If you’d like it to be a little sweeter, add a splash of St. Germain to your glass.