Out here in the land of non- Bangladeshi fish, try shrimp or any fresh-water fish cut into very small pieces.
After heating the oil add all the powder/paste spices and fry for a couple of minutes.

You might add a little bit of water if you are using powders only.

Make sure you don't burn the spices. (Include the onion pastes) Add the shredded onions and the fish. Add 1/2 cup of water and the salt.

Cover the dish and medium-hi heat. When the water has almost evaporated, add tomatoes, cilantro, and the onion leaves. Heat under low-medium heat till the oil starts to float.