This fish is amazing. You can also make it with chicken, but since fish and chicken cost about the same amount here, and since fish is always easier to deal with, I do fish.
About 3/4 kilo fish fillets
Lime juice and salt
2 T oil
1/2 onion, sliced
2 cloves garlic, minced
1 large poblano's worth of rajas
1 cup crema (it would be better to use cream instead of sour cream here)
Rinse the fish, set it on a plate, sprinkle with salt and lime, cover, and stick in the fridge for an hour, or as long as you have.
Heat 1 T oil and cook the onions till they're lightly browned, then add the garlic and rajas and cook 2 minutes, then add the crema and cook a bit longer till it's a lovely sauce. Add salt to taste. Cook the fish in a different skillet with the rest of the oil, then spoon the sauce over the top to serve.
Or you can make it easier. After the garlic and rajas have cooked a bit, add the fish. Cook on one side and flip to finish cooking. Add the crema after you've flipped the fish. Add salt to taste and serve.