Prep the vegetables. Core the tomatoes and chop them into chunks.
Dice a small handful each of cucumber, pepper, and onion for garnish; set aside. Roughly chop the rest for blending.
Soften the bread. Splash a tablespoon of water over the torn bread to moisten. This helps it blend smoothly and gives the soup a creamy body without dairy.
Blend the base. In a blender, add tomatoes, most of the cucumber, pepper, onion, garlic, moistened bread, 2 tablespoons sherry vinegar, 1/2 teaspoon salt, and a few grinds of black pepper.
Blend until very smooth, 45–60 seconds.
Stream in the olive oil. With the blender running on low, slowly pour in the olive oil. This emulsifies the soup, making it lush and slightly thicker.
Taste and adjust. Add another splash of vinegar if you want more brightness. Season with more salt and pepper as needed.
The flavor should be lively but balanced.
Chill. Transfer to a pitcher or bowl, cover, and refrigerate for at least 1 hour. The chill time lets the flavors marry and improves the texture.
Serve with texture. Ladle into bowls. Top with the reserved diced vegetables for crunch.
Drizzle with a little olive oil and add herbs or croutons if you like.