Make this New York City classic hotdog topping at home and enjoy delicious New York street food whenever you want. Warm your bun, put in your dog, squirt on some mustard, and add these onions. Yummy!
Heat the oil in a large saucepan over medium heat. Sauté the sliced onions in oil for 5 minutes, until the onions are soft but not brown.
Add 3 cups of water, corn syrup, corn starch, tomato paste, salt, and pepper flakes and stir. Bring to a boil, then lower the heat and simmer for 45 minutes.
Add vinegar. Continue to simmer for an additional 30 to 45 minutes or until most of the liquid has reduced and the onion sauce is thick.