In a large pot or saucepan, melt the 2 tablespoons of unsalted butter over medium heat. Once melted, add the thinly sliced onion and sauté until it turns golden brown, about 5-7 minutes.
Introduce the cinnamon stick, smashed cardamom pods, whole cloves, and bay leaves to the pot. Stir gently for about 1 minute until the spices release their delightful fragrances.
Add the rinsed and drained basmati rice to the pot, along with the teaspoon of turmeric and the 1/2 teaspoon of salt. Stir gently to coat the rice with the buttery spice mixture.
Pour in the 2-1/2 cups of boiling water, ensuring everything is well mixed. Bring the mixture to a boil.
Once boiling, reduce the heat to low and cover the pot with a tight-fitting lid. Let the rice simmer for about 15-20 minutes, or until all the water is absorbed and the rice is tender.
After the cooking time, remove the pot from heat and let it sit, covered, for an additional 5 minutes. Then, remove the lid, fluff the rice gently with a fork, and discard the whole spices.