Knead the dough ingredients together thoroughly and then leave to rise for at least 40 minutes. Peel the asparagus, if necessary, and then cut diagonally into 3-4cm lengths. Melt the butter in a frying pan, add the lemon juice, sugar and asparagus, and braise for 5-10 minutes until tender. Stretch the risen dough out into 20cm discs, place the asparagus in the middle, fold in half, and press the edges together or roll them in. Place in a hot oven (200°C) and bake until golden brown.