Make the curry blend by mixing the turmeric, ginger, coriander, cardamom and cayenne in a small bowl and set aside.
Prepare the rice by your preferred method. (We have a rice cooker that makes the job pretty foolproof, but when we want the rice to be extra savory, we substitute chicken stock/broth for the salted water, and that means we basically make a pilaf: rinse the rice until the water runs clear and drain. Heat a tablespoon of oil in a large sauce pot over medium-low heat, add the rice and toss, cooking until the rice begins to turn slightly translucent. Add 3 1/2 cups of warm water and 1 tsp of sea or kosher salt, or use chicken broth and omit the salt. Bring up to a boil then reduce to a simmer on medium-low. Simmer until the liquid is absorbed, about 15 minutes, then remove from the heat and cover. Let the rice stand 5 minutes, then fluff with a fork. Taste and season if more salt is needed.).
In a large frying pan or wok, heat the 2 Tbls oil and 2 Tbls butter on medium-low heat. Do not let the butter burn. When the butter stops giving off steam (you've made a simplified form of ghee), add the onion and curry blend.
Sweat the onion (i.e. cook it until it turns translucent) about 5 minutes. It's okay to get some browning with the onion if you like, but don't caramelize them too heavily.
Add the rice and turn up the heat to medium. Toss thoroughly to distribute the curry evenly.
Keep a close eye on the rice as it fries and stir to prevent sticking, but don't stir constantly as this will dry the rice and break it up, preventing it from browning. If you have trouble with sticking, add a bit more oil (not butter). The less you stir, the more it will brown, but the greater the chance of sticking.
Fry to your personal preference, stirring as needed. Some folks want to just give it a quick fry and serve right away, giving you more tender rice. We prefer to cook it a bit longer so we get a little browning, giving us a nice mix of crunchy bits with the more tender grains. But if you like your fried rice chewy, cook it even a bit longer, however beware cooking it too long or you'll get delicious curried buckshot!
Garnish with slivered green onion (optional).