put the chopped up onion and oil into a saucepan, use stainless steal pan or glass
saute until soft, then add carrots and water
heat to a boil and simmer until carrots are tender, then take off the heat
add chiles, lime juice, and salt, the put in a blender and puree
pour into sterilized jars and seal
Keep it in the refrigerator.
This stuff should -- theoretically -- keep for a couple of weeks. But it you are in doubt, toss it out and make a new batch. It's not like it takes long to make.
I found a similar recipe in a book by Nancy and Jeffrey Gerlach, called Too Many Chiles!, published by Out West Publishing in 1994. If you can find a copy, get it. It has lots of recipes and tips for dealing with chiles.