It is a lovely sunset, Raphael.
Maybe an application of a good Noise Reduction program would give it an even more smoothed out appearance throughout the sky area.
I know it's not particularly noticeable except for a small area at the very top, but it's also there throughout the image, and that would be removed as well.
You'll then notice the clear separation in tones of every tiny cloud formation and sky.
Golden sunset. Must quite an experience seeing and taking photo as the sun goes down there. 'Would be given spike if dim lighted architectures were included.