In a small microwave safe bowl, combine onions and garlic and microwave for about a minute or two until onions are soft and translucent. Set aside.
In a medium bowl, add all the ingredients: ketchup, vinegar, lemon juice, chili, brown sugar, honey, Worcestershire, mustard, paprika, molasses, pepper flakes and celery seeds. Finally add in the onions and garlic mixture.
Mix together until fully combined.
Place in an air tight container or jar and store in the fridge until ready to use.
Please keep in mind that nutritional information is a rough estimate and can vary greatly based on products used.