Heat oil over medium-high heat in a large skillet, and cook and stir onions until golden brown, about 8 minutes. Stir in tomato and cook for 2 minutes. Stir in garlic paste, turmeric, garam masala, green chile peppers, and salt, and cook for 2 minutes more.
Reduce heat to low, add the shrimp, and cook and stir over low heat until the shrimp are bright pink on the outside and the meat is no longer transparent in the center, about 8 minutes.
Add a small amount of water if needed; the sauce should be thick.
