Heat 2 tablespoons oil in a large saucepan over medium heat. Saute onions until tender. Stir in rice and brown slightly. Add 3 1/2 cups water, and half of the lemon juice. Reduce heat, cover and simmer for 20 minutes, or until all liquid is absorbed and rice is tender. Stir in dill, parsley and pine nuts.
Remove stems from grape leaves and place 1 tablespoon of rice mixture in the center. Fold in the sides and roll tightly. Place, folded side down, in a baking dish and cover with remaining olive oil, lemon juice and enough water to cover 1/2 of the dolmathas.
Cover with aluminum foil and bake in preheated oven for 45 minutes.