Cut the orange part of the peel in such a way that you don't remove the white part. White part might make it bitter.
Heat a tsp of oil and fry the sliced orange peel in it, till it crisps up. Then remove, and roughly chop it.
Temper the oil with curry leaves, mustard, cumin and fenugreek seeds. Add the chopped tomatoes and let it cook.
Once the tomatoes are softened, add the spice powders, fried orange peel and continue cooking
Add water as required and jaggery powder. Once it comes to a thokku consistency, turn off heat and stop the cooking.
Serve with dosa, idli, paratha, curd rice, etc.