Soak the cedar plank in water for at least one hour or overnight.

Fill a rimmed baking sheet three-fourths of the way with water, add 1/4 cup salt, and mix until the salt is fully dissolved.

Place the salmon skin side up in the salt bath and soak for five minutes. Remove and set aside.

In a saucepan, combine the maple syrup, vinegar, and bourbon over medium heat. Bring to a boil and cook for 10 minutes, or until it reduces by half. Remove from the heat and set aside.

In a bowl, mix together the garlic powder, paprika, chili powder, salt, and pepper. Sprinkle over the salmon.

Use a pastry brush to spread some of the glaze over the salmon, reserving the rest for grilling.

Heat the grill to medium heat (approximately 400 degrees Fahrenheit). Place the soaked plank over direct medium heat and close the lid. After five to 10 minutes, when the plank begins to smoke and char, turn it over.

Place the salmon on the charred side of the plank and grill for 20–25 minutes, brushing with the reserved glaze every five minutes or so.

Place the jalapeños in a baking pan. Sprinkle with salt, drizzle with oil, and grill for 10–15 minutes. Scatter the jalapeños and scallions over the salmon and serve.