Wash the spinach and chop it finely. Add 1 tablespoon salt and rub it with the hands. Leave for an hour. Squeeze it well. Add 1/3 cup olive oil, the onions, the feta cheese crumbled, eggs, parsley, dill and pepper.
Take a buttered baking pan and line with one pastry sheet. Brush it liberally with oil. Add 6 more pastry sheets, brushing each with oil, and let them come up the sides of the pan. Spread the spinach filling evenly and cover with 6 more pastry sheets, brushing each with oil. Brush the top with oil and score the top three sheets into 3 inch strips from one end of the pan to the other. Sprinkle the top with water, to prevent the pastry sheets from curling upwards.
Bake the spinach pie in a moderate oven for 40-45 minutes. Cool slighlty, cut into squares and serve either hot or cold. Make about 20 pieces.