Rinse long-grain white rice under cold running water in a fine-mesh sieve until the water runs clear; drain well.
Heat olive oil or unsalted butter in a medium pot or Dutch oven over medium heat.
Add diced yellow onion and cook, stirring occasionally, until translucent, about 5–7 minutes.
Add minced garlic and cook for 1 minute; stir in ground turmeric and ground cumin (optional) and toast spices for 30 seconds.
Add drained rice and stir to coat with oil and spices; cook for 2–3 minutes, stirring occasionally, until edges of grains look translucent.
Pour in chicken broth (or vegetable broth), add salt and bay leaf (optional), stir, and bring to a rolling boil.
Reduce heat to low, cover tightly, and simmer undisturbed for 15 minutes.
Remove from heat, keep lid on, and let rest for 10 minutes; discard bay leaf, fluff rice with a fork, and serve.