Hwy 101 north of Florence or south of Yachats. The best vantage point is on the Cape Creek bridge just before it enters the tunnel. Park on the north side of the bridge -- there is a walkway on the bridge!
Winter is the best time here. The light is dramatic between storms and the fog is at a minimum.
I was driving home from Newport, Oregon to my home in Florence when this sunset appeared out of the winter sky just as I was passing the lighthouse. I parked at the north end of the bridge and walked across it until I found the perfect angle to catch the sunset and the lighthouse. Right place and right time!