Take your roughly chopped onion, bell pepper, cucumber, jalapeno, and cilantro into a blender. Add tomatoes and pulse until it is pureed. Add the watermelon now, and pulse again until smooth. Pour this into a large bowl.

Taste the gazpacho and add the red wine vinegar to help balance the sweetness of watermelon and the tomatoes. You may need more or less vinegar depending on the sweetness and acidic levels of the watermelon and tomatoes. I would start with 1/4 cup of vinegar. Whisk in salt and olive oil once done balancing.

Now stir in the finely chopped onions, bell pepper, cucumber, and jalapeno. Chill this for at least an hour so that the flavors have time to blend. Add more salt if needed.

Now garnish to your liking using sour cream, diced avocado, and cilantro.