Can you use the entire preserved lemon or is it just the colored rind?
I was reading David Lebovitz's recipe, and he notes that the pulp of the lemon should be scraped out, maybe juiced, and then the innards should be discarded.
That's what I've read elsewhere, too. Rinse, then scrape off and discard the pulp, using just the peel.
I rinse and discard the pulp but I have heard that others use it. Without rinsing it's extremely salty. With a light rinse they are like extra concentrated lemon essence!