Clean, devein and wash the prawns well and keep aside.
Take the chilies and garlic pods into a mixer jar and blend them into a paste by adding little water.
Take the prawns in a mixing bowl and add the chilli garlic paste along with vinegar, turmeric powder and salt.
Add chopped or crushed ginger along with it.
Let the prawn marinate for close to 30 minutes.
After 30 minutes, heat the oil in a pan. Once it is well heated add the marinated prawn and roast it for about 5 minutes.
Drain the prawns and set them aside.
In the same oil, add the sliced onions and roast them well. You can even brown them if desired.
Add sliced tomatoes and cook until they become mushy.
Once done, add the prawns we roasted initially along with any juices from the marination.
Cover the pan with a lid and cook in medium flame for 5 minutes.
Remove the lid and add pepper powder according to your spice level.
Simmer for 5 more minutes or until you see the oil that's separated from the masala.