L'Étoile de Marrakesh on Rue de la Foire is one of the most reliable restaurants in Agadir for genuine Moroccan food at honest prices. The menu covers the standards well — lamb and chicken tagines, pastilla, couscous on Fridays — and the kitchen doesn't water things down for tourist palates. The decor is Moroccan-restaurant conventional (zellige tilework, carved plaster, lanterns) but the food is the point.
It's in the Talborjt area, away from the beach hotel zone, which means lower prices and more local clientele. Booking is advisable in the evening.