It's a variation of a chef's special at our favorite local Indian place and I think this is as close as I'm going to get to theirs.

1 Tablespoon oil
1 onion, sliced
4 garlic cloves, sliced
1 teaspoon coriander
1 teaspoon powdered ginger
1 teaspoon turmeric
1/2 teaspoon cumin
1 teaspoon chili powder
2 Tablespoons vinegar
1 pound medium size peeled, deveined shrimp
2 tomatoes, quartered
1/2 cup to 3/4 cup water
chopped fresh cilantro, for garnishing
Heat the oil in a large saucepan. Add the onion and garlic and saute over low heat for 5 minutes or until softened.
Combine coriander, ginger, turmeric, cumin, and chili powder. Add vinegar and stir into a smooth paste.
Add the paste to the onion/garlic and stir for 5 minutes, stirring constantly.
Next, add the shrimp and tomatoes, and stir until they're all well coated.
Stir in the water, cover and simmer for about 3 minutes longer. Sprinkle with cilantro.