Mix the semolina with the flour in a mixing bowl. Add the sugar, baking powder and lemon zest.
Place the vanilla pod on a chopping board, using a sharp knife, split the vanilla pod down the centre. Scrape the blade of the knife along the inside edge of the pod to remove the seeds and add to the beaten egg.
Using a round ended knife mix the low fat spread and egg into the flour, to form a soft dough. You may need to add a little milk to help the mixture bind.
Place the dough onto a floured surface and split into 4 parts. Roll each part into a long sausage shape, about 10cm in length.
Place onto a nonstick baking tray spaced apart.
Bake in a pre-heated oven for 15 minutes.
Remove from the oven and carefully lift the dough onto a chopping board.
Using a heavy chopping knife slice the dough at a 45 degree angle at 25mm intervals.
Place the cut biscuits back onto the baking tray and cook for a further 15 minutes until crisp.
Allow to cool then store in an air tight container.
To vary your biscotti flavours split the mixture into parts before baking and add almonds or hazelnuts.