what you need to do is to balance the exposure of the background and the foreground
1. a nice big reflector to bounce some of that nice bright sunlight back to the person or object (white/silver/gold depends on your desired effect)
2. if the reflected light is not enough to balance then add a fill flash
3. if that is still not enough and you must have that particular background, then come back when the sun is the other side and lighting the subject