Thinly slice the onion and beetroot. Chop the dill.
Lightly whisk the eggs with four pinches of salt.
Put the grill on.
Heat the oil in an oven-proof frying pan, then gently soften the onion (for about 5 minutes) at low temperature, then lay the beetroot slices over the onion, crumble the feta on top, then scatter the dill all over. Pour the egg mixture on top, allowing it to spread around the pan evenly. Put the lid on and cook for about 10 minutes until the egg has set.
Put the pan under the grill for about 2 minutes. until the top is golden.
Serve warm, cut into wedges, or at room temperature, diced.