Heat the oil in a medium size skillet over medium high heat. Add the rice and onion and sauté until both are translucent, about 5 minutes.
Stir in the water with 1 heaping tablespoon of tomato paste, bring to a boil, then reduce the heat to low and cover the pan. Simmer until the rice is just done, 20 minutes. Add salt and pepper to taste, and the nutmeg, if using. Sprinkle with the parsley, if desired. Fluff with a fork and serve.
NOTES: Not caring much for the flavor of plain water, a Greek cook who does not have stock on hand will usually flavor the water with tomato paste: about 1 tablespoon tomato paste to 1 cup water. This can be used for bulgur pilaf as well.
As with bulgur pilaf, the quantity can easily be doubled, tripled, or more: Use 1 1/4 times as much liquid as rice. Be sure to increase the amount of olive oil and onion as you increase the rice and liquid.