1. Heat a grill until medium-hot. Brush vegetables (except the cucumber) and garlic with oil; season with salt and pepper. Wrap garlic in foil. Grill onion, peppers, chile, and garlic, turning once, until soft and charred, 12 to 15 minutes; set aside. Grill tomatoes, turning once, until pale and skins peel, about 6 minutes. Transfer to a food processor; set aside. When cool enough to handle, peel garlic; cut peppers and onion into 1/2-inch pieces. Mince garlic and chile. Transfer all but tomatoes to a large bowl; add cucumber.

2. Thread shrimp onto skewers. Brush with oil; season with salt and pepper. Grill, turning once, until shrimp are pink and cooked through, 6 to 8 minutes.

3. Pulse tomatoes until slightly chunky; stir into vegetable mixture. Stir in cilantro, lime juice, shrimp, and 3 teaspoons salt; season with pepper. Garnish servings with lime wedges.