Submerge cedar plank in water and soak for 2-3 hours (may need to weight it down so it doesn't float).
When ready to start grilling, preheat grill on high heat for at least 10 minutes.
Place salmon skin side down. Score salmon flesh several times without cutting through to the skin.
Mix together olive oil, garlic, dill, salt, pepper and lemon zest.
Rub olive oil mixture all over salmon flesh and into scored areas.
When cedar plank starts to smoke, transfer salmon to hot plank and turn burners to low heat.
Keep spray bottle filled with water nearby to diffuse any flare-ups.
Cook until salmon registers 130 degrees Fahrenheit at its thickest point, using with a meat thermometer.
Remove from heat and let salmon rest for five minutes before serving.