Method:
Put 5 1/2 cups of the watermelon, 2 1/2 cups of the tomatoes, shallots, oil, vinegar, 2 tablespoons of the cilantro, salt and pepper into a blender and puree until smooth. Transfer puree to a fine mesh strainer set over a large bowl and strain puree, pressing as much through as possible; discard solids. Cover and chill for at least 1 hour.
Finely chop remaining 1/2 cup watermelon, 1/2 cup tomatoes and 2 tablespoons cilantro and toss together in a bowl. Pour chilled soup into bowls or glasses and top with watermelon-tomato mixture.