Rather than talk about a particular restaurant, I want to mention the food in general.
Try tajines, baked in a special bowl with a tented lid. Common varieties involve lamb or mutton or chicken, preserved lemons, olives, and spices. There are an enormous variety of olives here.
A large supermarket in the French quarter of Marrakech will provide staples, but go shopping in the souk as well! We bought some of the characteristic spice mixture Ras El-Hanut and added it to our home cooking. We also went to Berber markets in the mountains and bought local vegetables such as red leeks.