Indian Prawn Curry

While visiting a street market in Singapore's Indian district I learned a quick and easy way to make a savory Indian dish.

1 lb large prawns, peeled and deveined
2 Tbsp vegetable oil
1 medium onion, thinly sliced
2 Tbsp garam masala (you can buy at an Asian store or make it by using the ground spices common in Northern India)
1 tsp turmeric powder
1 tsp chili powder
2 large tomatoes, peeled and chopped
1 cup cold water
½ tsp salt
2 tsp fresh lime juice

Heat the oil in a pan and stir-fry the onions until it softens, 4-5 minutes.
While the onion is cooking, mix the garam masala, turmeric and chili powders with enough water to make a stiff paste. Add the spice paste to the softened onions and stir for another 2-3 minutes.
Add the tomatoes and cook until they soften and become pulpy. Add water and bring to boil, lower the heat and simmer, uncovered for another 10 minutes.
Add the prawns, salt and lime juice and simmer until the prawns are tender, approximately another 5 minutes.