Dry roast methi (fenugreek) and mustard seeds for 2-3 minutes until methi seeds turn golden brown on medium low flame.
Turn off the gas, cool completely, and blend to a fine powder.
In a kadai, add oil, mustard seeds, urad dal, curry leaves, red chillies, hing, garlic, and saute.
Add chopped tomatoes, salt, tamarind extract, and cook them in a medium flame until moisture from the tomatoes evaporates, takes about 8-10 minutes. Stir in between to avoid the masala from sticking to the kadai.
Once oil starts to separate add red chilli powder, mustard-methi powder ,adjust salt if needed and jaggery to the mixture and cook until oil oozes out of the tomato mixture.
Tomato thokku or tomato pickle is ready. Can be stored in the fridge for 2 weeks and without refrigeration for 3-4 days.