Secure the onion chunks and cherry tomatoes onto skewers.
Heat a grill to high, or heat a cast-iron grill pan over high heat. Line up the shishito peppers in columns crosswise to the grill lines, then add the skewers to the grill.
Grill the peppers for 8 to 10 minutes, turning once, or until their skin blisters and black marks form in zigzags on their