Quarter a watermelon. Remove the rind and chop the watermelon into squares.
In a small saucepan, add in the sugar, water and lemon juice. Heat over medium and stir until the sugar is dissolved. It took about two minutes for me.
Add the watermelon and simple syrup into a blender. Blend until smooth. Don't strain our the pulp.
Place the pureed watermelon into a bowl and place into the fridge until chilled. I let it sit for about 3 hours.
Place in the ice cream maker for the recommended time for your ice cream maker. Mine recommends no longer than 20 minutes.
Once it becomes slushy, place into a loaf pan. Cover with plastic wrap and place in the freezer overnight. This will allow the sorbet to firm up.
Scoop and serve. If the sorbet is too firm to scoop, let it sit out for about 10 - 15 minutes and then scoop.