what dose a real tandoori oven look like? and what makes them so special?

i pretty much get the same curry dish from my local every time, madras i just love it from there its the best around! its been the same chef for years and ive always try to copy his taste got close with help from this site but couldn't put my finger what i was missing! last night i had take out madras,
it was double lovely! but found some thing that ive never seen before half a slice of lemon peel?

 my only feeling is that this missed his blender?
 after i took a pic i had a bite all the bitterness i was expecting had gone and tasted just like the rest of the dish!
 im defo gonna try this in my next curry base, thought i let you guys know or even maybe its been tryed before?

i will upload a pic if i can find out how?

dose anyone have a bir madras recipe?  base sauce and main dish to cook at home without having to use massive quantities like 15 onions etc, many thanks unclebuck.