Heat the oil and fry the onion, lemongrass, garlic, capsicum and chilli for a few minutes. Add the rice, coconut cream, water and fish sauce and bring to a simmer. Cover, turn to very low and cook 10 minutes. Turn off the heat and allow to sit for 10 minutes.
Fluff the rice with a fork and add the lime juice. Check to see if it is salty enough; if not, add more fish sauce.