Put the chicken pieces in a 12-inch skillet (preferably nonstick) with a lid, along with the chopped onions, rosemary, and sage. Stir well to coat the chicken with the onion and herbs. Add enough olive oil to coat all of the chicken pieces, but not so much that it pools in the skillet. Sprinkle with 3/4 teaspoon salt and 1/4 teaspoon pepper.
Set the skillet over medium heat. Cook until the onions are very soft and the chicken and onions have turned golden brown, about 20 minutes. If the onion begins to brown too fast, turn down the heat. Add the wine and bring to a boil. Reduce the heat, cover the pan, and simmer gently until the chicken is tender, about 20 minutes. Squeeze the lemon over, taste for salt and pepper, and serve.