Preserved lemons in jars are available at Middle Eastern grocery stores, as is the super hot red pepper puree known as harissajust a few dabs will do.
In large nonstick skillet, heat oil over medium-high heat. Add bell pepper and onion and cook, stirring, until vegetables are just tender, about 5 minutes. Add garlic and paprika and cook, stirring, 1 minute.
Add tomato, salt, pepper and half of julienned lemon if using. Cook 1 minute, stirring. Add one-third of the mushrooms and cook, stirring, until they begin to release their juices, 2 to 3 minutes. Add another third of mushrooms and cook, stirring, 2 to 3 minutes. Add remaining mushrooms and cook until all mushrooms are tender, 3 to 5 minutes. Stir in parsley and cilantro and cook 1 minute more. Remove from heat.
Meanwhile, prepare couscous according to package directions. Mound couscous on large platter, surround with mushroom mixture and garnish with olives and remaining julienned lemon if using. Serve with a small dish of harissa if desired.