Meanwhile, place the butter in a medium saucepan set over medium-high heat. Once the butter has melted, add the onion and cook, stirring occasionally, until it begins to soften, about 5 minutes. Add the cardamom, cinnamon, and cloves, and cook, stirring, until the mixture smells very fragrant, about 1 minute. Stir in the coconut milk, water, and salt. Drain the rice through the sieve and add it to the pot. reduce the heat to low, cover, and cook until the rice has absorbed the liquid and is tender, about 15 minutes.