1/4 cup plus 2 tablespoons vegetable oil
2 bay leaves
1 one-inch piece of cinnamon stick
1 black cardamom pod
3 large Spanish or mild onions, thinly sliced
1 1/2 cups water
Heat the oil in a saucepan, add the bay leaves, cloves, cinnamon stick, and cardamom pod and cook for 1 minute over medium heat. Add the onion slices, lower the heat, and simmer until they are soft.
Add the water and bring to a boil, then reduce the heat and simmer for 30 minutes.
Remove from the heat and cool, then puree the sauce in a blender.