Special equipment: one 13-by-7-inch cedar plank, soaked for at least 1 hour
Preheat a grill to 350 degrees F over medium-low heat.
Combine the honey, lime juice, miso, soy sauce and garlic in a small bowl and blend well.
Place the salmon on the cedar plank and brush with the sauce to coat. Set the plank on the grill, cover and cook until the salmon just flakes with a fork, 20 to 25 minutes.
Toss the scallions and lemon wedges in the oil and season with salt and pepper. When the salmon has about 5 more minutes to cook, add the scallions and lemons to the grill and cook them until charred and softened.
Remove the salmon from grill, brush with more sauce and let sit for 5 to 10 minutes.
Serve the salmon with the charred scallions and lemons.