The streets around Atatürk Caddesi in Muratpaşa have the best concentration of traditional lokantas in the city — small, unpretentious restaurants serving set-menu Turkish food at midday: lentil soup, various stews (güveç), bulgur pilav, roasted vegetables, and a dessert. You point at what you want from the trays in the bain-marie, pay a fixed price per dish, and eat well for a few euros.
This is how working Antalya eats lunch. Lokantas typically open from around 11am to 3pm and close when the food runs out. They are the best value eating in the city by some distance.