In a different pot, add oil then cook your chopped onion till golden brown, add smashed ginger and garlic, let it cook then add tomato.

For tomato you can put the whole tomato to boil in your chicken then remove the outer skin and blend it before use, or your can just crate it

When it's ready add tomato past enough hot water and add your chicken one by one, you can also add little carry powder. Let it boil for 7- 10 min at a low heat

Enjoy