Preheat the oven to 375 degrees F (190 degrees C).

Heat 2 tablespoons oil in a large saucepan over medium heat. Sauté onions in oil until tender. Stir in rice and cook until lightly browned. Pour in 3 1/2 cups water and 1/2 of the lemon juice. Reduce heat, cover, and simmer until all liquid is absorbed and rice is tender, about 20 minutes. Stir in dill, parsley, and pine nuts; remove from heat.

Remove stems from grape leaves and place 1 tablespoon rice mixture in the center of each. Fold in the sides and roll tightly. Place seam-side down in a baking dish and cover with remaining olive oil, lemon juice, and enough water to cover 1/2 of the dolmathes.

Cover with aluminum foil and bake in the preheated oven for 45 minutes.