It's actually very difficult to capture a sunset "as you see it", as a camera has much less dynamic range than your eye. What this means is that those dark green trees you see in the background will be completely black when recorded on your camera's sensor (if you meter for the sun), and that beautiful red sunset will be almost completely white if you meter for the trees.
Basically, you can't capture a sunset exactly as you see it, but I would switch to Center-Weighted metering, and meter for the sky. If you want to recompose, be sure to exposure-lock the sky first. Hopefully, it will come out OK. Best of luck!