1. Preheat grill to medium-high.
2. Grill tomatoes and bell pepper whole, turning a few times, until they soften and the skins are blistered and charred in spots (8 minutes).
3. Cover the pepper with foil and let sit until cool enough to handle. Peel off the skin, cut the pepper in half, and discard the stem and seeds. Place half in a blender or food processor.
4. When the tomatoes are cool enough to handle, core and chop. Add the tomatoes to the blender or food processor.
5. Add half the cucumber and remaining ingredients to a blender or food processor and blend until smooth. Refrigerate until room temperature or chilled, at least 1 hour.
6. Finely dice the remaining cucumber and bell pepper. Stir into chilled gazpacho to serve.