For the quick preserved lemon: In a small saucepan, combine lemon, lemon juice, and salt. Bring to a simmer and cook until lemon is soft, approximately 15 minutes. Cool, then chop. Set aside
For the shrimp: Preheat the oven to 400 degrees F.
In a heavy-bottomed skillet over medium heat, add the oil followed by onions, garlic, and tomatoes. Gently cook, stirring, until vegetables are fragrant, about 3 minutes. Add the ras el hanout and salt and roast in the oven 5 to 7 minutes. Remove from the oven and fold in chopped preserved lemon.
Arrange shrimp over the tomato mixture in an even layer. Drizzle with olive oil and place in the oven until the shrimp are cooked through and are bright coral pink, about 2 minutes. Remove, top with chopped cilantro and serve.