Preheat oven to 375 degrees F. Place half a chopped onions and all the carrots in an 11x8-inch baking dish.
Lay the chicken pieces over the onions and carrots. Season with salt and pepper. Place the garlic and remaining of onions on top.
In a small bowl mix together the orange juice, lemon juice, 2-tablespoons sugar and mustered. Pour over the chickens (chickens should be covered with the orange juice mixture, add more orange juice if needed).
Bake in preheated oven for 55-60 minutes. Remove from oven.
Then remove leftover sauce from baking dish and pour into a saucepan. Add the flour and cook over medium heat until the sauce thickens, stirring constantly.
Place the butter on top of the chickens and sprinkle with 1-teaspoon sugar.
Return to the oven and bake for 15 minutes.
Remove chicken from oven and place on a serving dish. Pour the orange juice sauce over the chicken and serve.