Wash and cut the tomatoes into chunks.
Peel and chop the onion into chunks.
Peel the garlic cloves.
Peel the ginger and cut into pieces.
Heat oil in a wide pan over medium heat.
When the oil is hot, add fenugreek seeds. Then add the mustard seeds.
Add the chana dal and roast for about a minute, stirring all the time.
Then add the urad dal. Keep stirring till the dal begins to turn light brown in colour.
Add the dried red chillis. Sti fry for a few seconds.
Add the chopped onion.
Stir fry the onion till it becomes a bit soft.
Add garlic and ginger. Stir fry the mixture for a minute or two.
Add the tomatoes, turmeric powder and salt.
Mix well.
Allow the mixture to cook over medium to low heat till the tomatoes are soft and mushy.
If there is too much liquid, increase the heat and allow it to evaporate. Don't make the tomato mixture completely dry. It should appear moist.
Add the jaggery if using any and mix well.
Allow the mixture to cool down a bit.
Transfer the tomato mixture to a blender jug.
Puree the mixture to a smooth consistency.
Remove the tomato onion chutney into a serving bowl.