Preheat the oven to 220°C bake (200°C fan bake). Line baking tray with baking paper.
Gently unroll pastry onto a lined oven tray. Use a sharp knife to lightly score around the border of pastry 1cm from the edge (not cutting all the way through). Using a fork, prick pastry in a few places inside the border. Brush the border area with a little of the beaten egg.
Place the remaining egg into a bowl with the ricotta, Parmesan, lemon juice and zest. Season with salt and pepper and mix well to combine.
Spread the ricotta mixture over the pastry sheet, staying within the marked border. Cut asparagus spears in half and arrange them on top.
Bake on middle-upper oven rack for about 10-15 minutes, until puffed and golden brown.
Sprinkle with the chilli flakes and extra Parmesan. Slice and serve.