Grilled Chicken Tacos

INGREDIENTS

• 1 medium onion, cut into wedges, keeping root intact
• 2 garlic cloves, finely chopped
• 1 skinless, boneless chicken thighs
• 1 cumin seeds, coarsely crushed
• 1 vegetable oil
• 1 kosher salt
• 1/2 freshly ground black pepper
• 8 corn tortillas, warmed (for serving)
• 2 avocados, sliced (for serving)
• (click for recipe; for serving)
• Cilantro sprigs, sliced radishes, and lime wedges (for serving)