After staying in Rabat for a month and eating out as much as possible (also can be read as: "every night because I was too lazy to cook and buy the things necessary for cooking"), I think I can safely give my top choices for eating out in Rabat. (Sorry for the picture quality, most of these photos were snapped quickly on my phone!)
You most likely will not be able to leave Rabat without going to one of the Dar Naji locations (there is one in the medina and one in the modern shopping area of the city), and it doesn't disappoint. Moroccan and Berber food at good prices, they ensure that their guests also have a full culture experience with beautiful decorations, live music, and waiters with fancy tricks up their sleeves. People say the location in Agdal is prettier, but the food in the medina is better. I say go where your heart desires.
If you feel like going fancy, this is the best place for a Moroccan meal. There are set menus to choose from, ranging from 25-35 euro a plate (but you will be thoroughly STUFFED). Of course, the inside is decorated with colorful Moroccan rugs and tapestries, even the bathroom is a site to see. This was my favorite meal in Rabat and worth the splurge!
Sandwich Street Food
If you're standing facing the outside of the Gare Rabat Ville (the main railway station on Mohammed V), go around to the left and walk down the right where the tram stops. Right past the tram stop on the left is a man who makes amazing sandwiches. I do not know all the options, but you can get one with eggs & cheese or a fish sandwich filled with vegetables & cheese. (If you don't speak Darija or any Arabic, you might want to have some pictures on your phone to show what you want :))
If you're getting tired of Moroccan food, but still want something that you're (maybe not) accustomed to, head over to the famous Syrian restaurant of Rabat, Yamal Acham. No matter when you go at night, there will always be a line. Sometimes you only have a 10 minute wait, sometimes an hour, but it's worth it. Besides street food, this is one the cheapest & best places to eat in Rabat -- we paid about 22 euro for six of us!
If you happen to be French and you're thinking, "ugh, I just need some homestyle comfort food", there is an amazing French restaurant in Rabat. Their main focus is crepes, but there are some other options. And, it's a good place to sit in the garden and sneak a wine!
If you're American and looking for that national comfort food, Bistrot Burger in Agdal has a cute environment and can saturate your needs! I personally am obsessed with their black risotto & delicious juices.
Not a place to eat, but it can't be missed. You can pop in Cafe Marue for an afternoon tea & snack, with a terrace overlooking the ocean and the beaches of Rabat and Salé, it's the perfect place to enjoy the sun.