The Roque de Los Muchachos is a spectacular place to watch the sunset. For one thing, you’re usually above the clouds (which is one reason the observatory is there.)
For another, very shortly before sunset, you can see the shadow of the island itself growing eastwards over the cloud sea.
And of course, you’re surrounded by the telescopes. If you’re not used to them, they look surreal and science-fictiony. And all the domes are painted white or silver. This is to reflect heat, but it makes them very photogenic at sunset, or indeed by moonlight.
The road to the Roque is closed at night because tourists cause local light pollution. Several of the telescopes could spot the light of a candle on the moon, so hand-held torches and car headlights are a big problem. Even side-lights are enough to sugar up the observations of the MAGIC telescope. So the road closes shortly after sunset, but the site’s night watchman goes around to chivvy people out. You’ll have to leave before most of the stars come out, but you have a good chance of seeing the moon and Venus.
And then, I’m afriad, you’ll have to drive down all those bends in the dark.