The problem is the amount of dynamic range your camera's sensor can cope with. If you have a lot of sky in the picture, then the metering system will expose for that, leaving the foreground dark. If you have too much of the foreground, then the sky is blown out.

This is quite normal on dark days and especially dark times of the day, like sunset and sunrise. You have to accept mostly what you want to show in the picture, the gorund or the sky.

For sunsets, get the camera to expose for the sky, don't point the camera at the sun until it is well down and red, or you'll risk damaging the camera. That last point is much more important with a DSLR, as with an optical viewfinder, it'll be your eye that is damaged, permanently !!! The foreground will be dark, but that will enhance the picture.

Most important, a lot of cameras on auto white balance will try to correct the red back to normal daylight, resulting in washed out colourless sunsets. Set the white balance to "cloudy", that usually gives the best reproduction of the true colours at sunsets. But don't be afraid to experiment, try the "shade" setting too, it often brings out the reds in sunsets a lot better. Try all the white balance settings until it looks right for you

If you have a camera that can save files in RAW, then use that setting, at least for sunsets Using RAW allows you to change the white balance settings later on your PC, trying different settings on the same picture until it looks right.

Regards,

Brian

A few samples never hurt. I took these a few weeks ago, in Botswana. OK Botswana sunsets are great anyway, so I have the advantage on you, but the principle is the same