New York Pushcart Onions (For Hot Dogs)

2 tablespoons vegetable oil

2 onions, sliced into 1/4-inch thick rings

½ green bell pepper, thinly sliced

¼ cup ketchup, or more to taste

½ teaspoon white sugar

⅛ teaspoon chili powder

1 dash hot pepper sauce

1 pinch ground cinnamon

1 cup water

Heat vegetable oil in a large skillet over medium heat; cook and stir onions and green bell pepper until onions are slightly browned and soft, 8 to 12 minutes. Mix in ketchup, sugar, chili powder, hot pepper sauce, and cinnamon until thoroughly combined. Pour in water, bring mixture to a boil, and simmer uncovered until onions are tender, about 10 more minutes.