Directions

1. Heat oven to 170C/150C fan/gas 3-4 and place the turkey in a large roasting tin. Tuck 3 of the onion halves and the lemon quarters into the cavity and season. Cover with foil, make sure there's plenty of space between the turkey and foil for the air to circulate and seal the edges tightly so that no steam escapes. Roast for 4 hrs.
2. Meanwhile, finely chop the remaining onion half, and mix with the butter and sage. Take the turkey out of the oven and raise the temp to 200C/180C fan/ gas 6. Brush the sage and onion butter all over the turkey and return to the oven, uncovered, for 45 mins until crisp and dark golden. If you're making the roasties, then start them in the oven when the turkey goes back in, uncovered.
3. Transfer the turkey to a warm serving plate, cover loosely with foil and leave to rest for 30 mins. Tip the juices out of the pan into a bowl, leave for a moment to settle, then scoop the buttery oil from the surface into a separate bowl. Spoon 2 tbsp of this oil back into the tin and return to the heat.
4. Stir the flour into the tin using a wooden spoon, scraping the residue off the bottom of the tin as you go. Cook for 2 mins, then stir in the Marsala or Madeira and bring to the boil. Make the reserved turkey juices up to 500ml using hot chicken stock and pour into the tin. Bring to the boil and simmer for a few mins, then add cranberry jelly. Keep warm until ready to serve.