Adapted from WeAreNotMartha , who in turn adapted it from Madhur Jaffrey’s Indian Cooking
Vindaloo spices (we used some from our India trip. If putting together yourself, see the process at WeAreNotMartha
5 T white wine vinegar
1 t light brown sugar
10 T vegetable oil
2 medium onions, peeled and sliced into half-rings
1 1/3 C water