Soak the cedar plank in cold water at least 2 hours. Combine the tequila, citrus zest and juice and sugar in a side dish. Add the salmon and turn to coat. Cover, marinate and refrigerate the salmon 1 hour, turning occasionally.
Preheat your barbecue to medium-high. Remove the plank from the water and pat dry one side. Set the fish on the dry side of the plank. Pour the marinade into a small skillet. Bring the marinade to a simmer and reduce until thick and syrupy. Brush this mixture on the salmon and season the fish with salt and pepper.
Set the plank on one side of the barbecue. Turn the heat underneath the plank to low and leave the other side of the barbecue set at medium-high. Close the lid and cook the salmon for 15 to 18 minutes, or until just cooked through. Keep a spray bottle of water handy in case the board ignites. Set the plank on a serving tray, garnish with lime slices and serve.