In a large saucepan, melt the butter over medium heat. Add the sliced onions and cook, stirring frequently, until they are caramelized and golden brown, about 15-20 minutes.

Season the onions with salt and pepper during the cooking process.

Once the onions are caramelized, add the uncooked rice to the saucepan and stir to coat the rice with the butter and onions.

Pour in the chicken broth and bring to a boil. Reduce the heat to low, cover, and simmer for 15-20 minutes, or until the rice is tender and the liquid is absorbed.

Remove the saucepan from heat and let it sit covered for 5 minutes. Fluff the rice with a fork.

Stir in the grated Parmesan cheese if using, and garnish with chopped parsley before serving.