Remove sautéed diced onion with slotted spoon and place into mixing bowl.
Into at least 2 tbsp bacon fat, cook 2 tbsp flour until smooth and bubbly, add 3 tbsp vinegar and 2 teaspoon sugar, 1 tsp salt, and enough water to make a medium sauce (about 1 cup or more).
Bring to a boil and cook until sauce is thickened.
Pour over ingredients in mixing bowl, and toss and mix.