Preheat oven to 200°C or 180°C fan. Lightly grease a 25cm-deep pie dish.
Cut tough white stalks from silverbeet. Rinse green leaves well and steam over a saucepan of simmering water for 3 minutes, until wilted. Drain well and chop finely. Drain in a colander, pressing well to remove any remaining moisture.
Heat oil in a frying pan on medium and cook onion for 3 minutes, stirring, until soft but not golden. Add silverbeet and cook, stirring, for 5 minutes. Season to taste and set aside to cool. Crumble fetta into a bowl and combine with egg, green onion and parsley. Stir in silverbeet mixture.
Brush a sheet of filo pastry with a little melted butter and line prepared dish. Top with six more sheets, brushing each with melted butter. Spread last layer with silverbeet mixture. Season with pepper and scatter with dill. Cover with remaining sheets of pastry, brushing each with butter as before. Press edges firmly together and trim excess pastry, using scissors. Brush top generously with butter. Bake for 1 hour, until pastry is golden. Serve hot or at room temperature.