Core and roughly chop the tomatoes: Peel and chop the cucumber, then seed and chop the red bell pepper. Roughly chop the red onion and peel the garlic.

Place the torn bread in a large bowl: Add several spoonfuls of juice from the chopped tomatoes and let it stand for 5 minutes. The bread should soften completely without becoming soupy.

Add the tomatoes, cucumber, bell pepper, red onion, garlic, and softened bread to a 64-ounce (1.9 L) blender. If the ingredients do not fit comfortably, blend the vegetables in two batches and combine them afterward.

Blend on low speed for 20 to 30 seconds, then increase to high. Blend for 1 to 2 minutes, until the vegetables are fully broken down and the mixture looks smooth and evenly colored.

With the blender running on medium speed, slowly pour in the olive oil. Add the sherry vinegar, salt, black pepper, and cold water.

Continue blending on high for another 30 to 60 seconds. The gazpacho should look smooth, slightly creamy, and pourable. It should coat a spoon lightly without resembling a thick puree.

If the soup is thicker than desired, add additional cold water 1 tablespoon (15 ml) at a time. Blend briefly after each addition. Avoid adding too much water, which can dilute the tomato flavor.

For an especially smooth gazpacho, pour the soup through a fine-mesh strainer into a large bowl, pressing gently with a spatula. Discard the remaining skins and seeds. Skip this step for a more rustic texture.

Taste the soup before chilling: It should taste slightly more acidic and seasoned than you want the finished soup because cold temperatures soften flavor. Add a small amount of extra vinegar or salt only if needed.

Transfer the gazpacho to an airtight container: Refrigerate for at least 2 hours, until completely cold. Stir well before serving because slight separation is normal.

Shortly before serving, finely dice the optional cucumber and tomato. Keep the pieces small so they are easy to eat with a spoon.

Ladle the cold gazpacho into bowls or glasses: Top with diced cucumber, diced tomato, parsley, and a light drizzle of olive oil as desired.