Heat olive oil in a large skillet over medium-high heat. Saute onions in the oil until soft and translucent. Add spinach, and cook stirring for a few minutes, then pour in the tomato sauce and water. Bring to a boil, and season with parsley, dill, salt and pepper. Stir in rice, reduce heat to low, and simmer uncovered for 20 to 25 minutes, or until rice is tender. Add more water if necessary.