Preheat the oven to 350°F. Grease the bottom of the 9×13 inch baking dish lightly.
Lay the sliced sweet onions in a single layer across the entire bottom of the prepared baking dish.
Position the chicken thighs skin-side up over the sliced sweet onions in a single layer.
Evenly pour the Russian dressing over top of the chicken thighs using a spoon to ensure each piece is coated well with sauce.
Cover the baking dish tightly w/ aluminum foil. Bake in the preheated oven for approximately 45 minutes.
Remove the foil carefully. Spoon some of the pan sauce from the bottom of the baking dish over the chicken thighs.
Put it back into the oven without a cover. Bake an additional 25-35 min., or until cooked through & has reached an internal temperature of at least 165°F.
*Nutritional information is a calculated guesstimate. Please note that this can change with different brands and modifications you may make to the recipe. For the most accurate information, use a nutritional calculator with the exact brands and measurements you're using with each recipe.