Watermelon Martini

• 2 cups watermelon cubes
• 1 tablespoon sugar
• 8 ounces (1 cup) vodka
• 2 ounces (1/4 cup) fresh lemon juice, from about 2 lemons
• 12 to 16 ounces (1 1/2 to 2 cups) cold seltzer
• 1 lemon, cut into slices, for garnish (optional ... I didn't do this)

• Blend the watermelon cubes with the sugar
• Strain through a fine sieve
• You should have 1 1/4 cup of watermelon juice
• Add it to a pitcher or large measuring cup with the vodka and lemon juice
• Stir

• Distribute the mixture among 4 highball glasses
• Add three ice cubes to each
• Fill each to the brim with seltzer
• Mix to combine
• Garnish by slipping in a lemon slice or two (optional)