You don't mention in your post what type of rash you have. This would go a long way to enabling us to perhaps help you. If it is a definite lupus rash i.e. buttefly/malar, discoid, hives or any of the other rashes that is lupus associated. Whichever rash it is will determine what the treatment will be.
Also in some cases the rash that is presenting might not be anything to do with lupus at all. This can only be determined by a rheumatologist - preferably one who specialises in lupus.
As far as the word "cure" goes with anything lupus related, please forget it. People have a tendency to come out of the woodwork and start to prey on those of us who have chronic illnesses. As you know there is no cure for lupus, if there was we wouldn't need lupus doctors and all the medications we have to take and all of the wonderful sites like this one to be of help and support.
Maybe you could let us know exactly what type of rash you have? I am sure you will be able to get more information in this way.