Melt the butter in a large frying pan, add the sugar, wine and spices and heat gently until the sugar has dissolved.
Add the pears to the red wine mix and simmer until the pears are almost tender (about 5 minutes), turning until evenly coloured. Scoop out of the pan and set aside.
Increase the heat and simmer the mixture for 5 minutes or until it is reduced and syrupy. Turn the heat off, stir in the food colouring, if using, then return the pears to the pan and coat in the syrup. Leave to cool for 15 minutes.
Roll out the pastry on a lightly floured surface, then trim to a 25 cm (10 inch) circle. Tip the pears, syrup and spices into a buttered metal pie dish, 20 cm (8 inches) in diameter and 5 cm (2 inches) deep. Lay the pastry on top, tucking it down the sides of the tin. Make 4 small steam vents in the top with a knife, then bake (unglazed) in a preheated oven, 200°C (400°F), Gas Mark 6, for 30 minutes until the pastry is risen, has shrunk from the sides of the tin and the juices are bubbling.
Leave to stand for 5 minutes. Loosen the edges with a knife, cover with a large serving plate, then invert the tin.