The clay oven is the one piece of equipment that defines an Indian restaurant kitchen. It also shapes a surprising amount of the menu around it, for reasons that come down to physics.
Three kinds of heat at once
A tandoor is a thick clay vessel heated by a fire at its base and held far hotter than a domestic oven. The walls store an enormous amount of energy.
Food inside receives radiant heat from those glowing walls, convected heat from the rising column of hot air, and conducted heat where bread is slapped directly onto the clay.
No single mechanism dominates, and the combination cooks the surface very fast while the interior is still catching up.
Why speed produces the texture
Because the exterior sets and browns within a couple of minutes, moisture inside has little time to escape. Meat emerges charred outside and still juicy within.
A lower, slower oven reverses that balance. The interior dries out well before the surface develops comparable colour.
The marinade coating matters here too, since a yogurt layer dries into a crust that takes colour readily and shields the meat beneath it.
What the fire contributes beyond temperature
Fat and marinade drip from skewers onto the coals and burn, sending smoke back up through the chamber. The food is seasoned by its own drippings.
That circulation is confined by the narrow mouth of the oven, so the smoke concentrates rather than dispersing as it would over an open grill.
The effect is difficult to imitate in a kitchen where the heat source sits above the food or is fully enclosed and vented.
Why breads and meats share the chamber
Flatbread stuck to the wall cooks by conduction on one face and radiation on the other, puffing as trapped steam expands inside the dough.
The same heat that chars a skewer of meat in minutes bakes a naan in under two. Running both from one oven is what makes the combination economical.
It also means bread and grilled dishes are timed together, which is why they typically arrive at the table at the same moment.
How the oven shapes the menu
Because the tandoor is expensive to run and slow to heat, kitchens keep it lit throughout service and design the menu to use it continuously.
That gives rise to a whole section of skewered starters, and to the practice of pre-cooking meat in the tandoor before it enters a gravy.
Dishes built on that pre-cooked meat carry a smoky note into the sauce, which is a large part of why restaurant versions taste distinct from anything simmered from raw.