How to Make It
Combine 3/4 cup water and bread in a small bowl; let stand 10 minutes.
Heat a grill pan over high heat; coat pan with cooking spray. Arrange onions in pan; grill onions 90 seconds on each side or until charred and softened. Coarsely chop.
Combine bread mixture, yellow tomatoes, 3 tablespoons olive oil, vinegar, and next 5 ingredients (through serrano) in a blender; process until smooth. Place in a large bowl. Stir in green onions, red tomato, green tomato, zucchini, and 3 tablespoons cilantro. Cover and refrigerate at least 1 hour. Stir well before serving. Place about 3/4 cup soup in each of 8 chilled bowls. Top evenly with remaining 2 tablespoons each oil and cilantro.