Though this dish takes longer to prepare, it is certainly worth the wait. The cooking time is pretty less compared to the preparation time but the longer you marinate it, the better it will taste.
Mix the water, vinegar, brown sugar, rosemary, salt, pepper, and chili flakes in a bowl.
Place the onion slices in a baking dish and then pour the vinegar over it.
Cover and marinate onion slices overnight in the red wine vinegar marinade.
Preheat the oven to 200 degrees C, flip onion slices, and then brush them with butter on top of each slice. Bake it for 35 to 40 minutes or until it turns slightly dry on top. Serve and enjoy!
You can also use unpeeled onion slices to prepare this dish, but remember to remove the onion peels before serving.
Nutritional information (per serving): 42 Calories, 0.8g Total fat (0.5g Saturated fat, 0.1g Polyunsaturated fat, 0.2g Monounsaturated fat), 1.9mg Cholesterol, 153.3mg Sodium, 123.2mg Potassium, 8.5g Total carbohydrates (1.4g Dietary fiber, 4.6g Sugars), 0.9g Protein