Core tomatoes, then cut them in half crosswise to expose seeds. Gently squeeze out the seeds. Dice the tomatoes, onion, cucumber, bell pepper, and scallions. Stir together with remaining ingredients – except garnish– and refrigerate, covered, at least 2 hours.
Ladle the soup into serving bowls and decorate each with a dollop of Herbed Sour Cream, 2 cherry-tomato halves, and 3 golden-tomato wedges. Top with a sprig of cilantro and serve.
Herbed Sour Cream
Mix all ingredients together.