Peel the watermelon using a vegetable peeler if necessary, then cut it into chunks. Chop the tomatoes into smaller pieces and set aside.
Place 2 cups of watermelon chunks into a large saucepan and bring to a gentle boil over medium heat. Simmer for about 8-10 minutes until the watermelon softens and the liquid begins to evaporate slightly, creating a concentrated sweetness. Stir occasionally and monitor for bubbling.
Remove the saucepan from heat and allow the cooked watermelon to cool slightly, about 5 minutes. Transfer the cooked watermelon to a blender along with the raw watermelon chunks, chopped tomatoes, salt, and black pepper. Blend until smooth and creamy, about 30-60 seconds. Adjust seasoning to taste.
Pour the blended soup into a large bowl or container and refrigerate for at least 2 hours to chill thoroughly. The soup should become vibrant in color and velvety in texture.
Serve the chilled soup in bowls, garnished with a drizzle of olive oil and a sprinkling of chopped herbs. Optionally, add a few fresh tomato slices or watermelon cubes for visual appeal.
