Melt butter in a large skillet over medium heat. Sauté onion in butter until tender and it begins to turn golden in color. Add rice and sauté, stirring, until onions begin to brown. Add chicken broth and bring to a boil. Stir in salt, pepper, and cinnamon. Transfer to a covered baking dish or leave in the skillet if it is ovenproof. Cover and bake at 350° for 1 hour, until rice is tender.