Place your red onion into a small bowl, together with vinegar and 1/2 cup of cold water.
Grate your heirloom tomato until you have approximately 1 cup of tomato juice. Add this to a very large bowl, together with your garlic. Cut the remaining heirloom tomato into large chunks and add to bowl.
Next, add stale bread (cut into 1-inch cubes) into large bowl with tomatoes, together with cucumber, peach, cherry tomatoes, and fresh basil. Add the red onions.
Season with salt, pepper, and Italian seasoning. Drizzle with olive oil. Mix all the ingredients until well combined.