Preheat the oven to 180°C.
Mix salt and egg whites in a bowl until a firm, cement-like consistency is achieved.
Coat beetroot in the salt mixture, place on a tray, and bake for one hour.
Remove the salt crust after cooking, then peel and slice the beetroot.
Roast courgette, fennel, and garlic in olive oil with thyme for 15-20 minutes.
Increase the oven temperature to 200°C.
Brush the edges of the puff pastry sheet with beaten egg.
Place roasted vegetables, beetroot, tomatoes, and crumbled cheese onto the pastry center.
Drizzle with additional olive oil and season with salt and pepper.
Bake for 20 minutes until the pastry is golden and crisp.