French Onion Rice

In a large pot over medium heat, melt 3 tablespoons butter and olive oil. Add onions and salt and cook, stirring frequently, until caramelized, 35 to 40 minutes. Transfer to a bowl. To pot, melt 1 more tablespoon of butter, then add garlic, thyme, and pepper and stir until fragrant, 1 minute. Add in wine and let cook until mostly evaporated. Add remaining 2 tablespoons butter and let melt. Add in rice, stirring until grains are toasted, 3 to 4 minutes. Return ¾ of the caramelized onions to pot, reserving the rest for topping, and stir to combine.  Stir in broth, bring to a boil, then reduce heat to low and cover. Simmer until rice is tender, about 18 minutes.  Remove from heat, and let covered pot stand for 5 minutes before removing the lid. Fluff rice gently with a fork. Top with remaining caramelized onions, Gruyère, more thyme, and a squeeze of lemon, if desired, before serving.