Bring water, coriander seed, lemongrass and salt up to a boil. Rinse rice in a fine strainer until it runs clear and add to boiling water. Simmer rice (uncovered is OK) for 10 minutes. Drain and rinse rice through a fine strainer, remove lemongrass and return to pot.
Over low heat stir in olive oil, lemon zest and lemon juice until blended. Stir in chopped coriander and red chili flakes (if using) and season to taste.