Shooting into a setting sun can be tough, and not always smart. Tough because it can be hard to focus, plus the brightness of the setting sun can really throw off your exposure. And not always smart because, well, you are pointing a magnifying class into the sun and can fry your eyeballs and/or camera sensor. (Clearly I am not smart, since I do it all the time).
As for the exposure part, there is an easy solution. The problem is the bright sun tricks your camera into thinking there is plenty of light, so it underexposes the image, leaving you with a round sun and a dark, murky, blood-red picture.
There are several solutions.
You can put the camera on manual and spot meter off the area of the sky to the side of the sun itself, then overexpose a bit to get nice pastel colors.
Or just point and shoot as usual and then use your exposure compensation dialed in to overexpose until you have it how you want it (assuming you are shooting digitally!). (Some cameras are kind of smart about hot spots like that and take it into partial account.). I used the latter approach here, overexposing over 1 stop.
Backlit purple thistle at sunset, Great Trinity Forest, Dallas, Texas, USA. Canon 1Dx. 560mm. ISO 800. 1.320 sec. at f. 22. Aperture Priority. Matrix Metering. EV +1 1/3.