The secret recepie of a great sunrise or sunset is that the sky is covered in clouds that are high, but also thick enough to produce strong contrasts between the highlights and the shadows. Farther away in the direction of the Sun the sky has to be clear enough to allow sunlight to illuminate the bottom of the cloud. Here the cloud in qustion is Altocumulus stratiformis. It’s quite a common cloud, and thus also the most common culprit of spectacular vistas such as these. Cirrus spissatus is also a great candidate, although that one is a bit rarer and doesn’t usually form expansive sheets such as here.