Wash the pears, halve them and remove the seeds. Put them in a tray with just a little water, sprinkle on the sugar and add the cinnamon and cloves. Put them to bake in a moderately heated oven, stirring regularly.
Leave the jam in the oven until the point when you can take a wooden spoon, run it along the tray's bottom and it leaves a trail. Finally, mix in 1 teaspoon citric acid, and after 4-5 minutes, the roasted pear jam will be ready.
Discard the cinnamon stick and cloves and pour the still hot jam in jars, close and turn them upside down until completely cool.