Start by greasing and lining the base of a 20cm cake tin with parchment paper. Preheat the oven to 160°C fan/180°C.
Begin by caramelising the pears: peel, core and slice the pears into eighths. Then in a heavy based frying pan heat the butter with the sugar, maple syrup and ground ginger. as soon as the mixture melts and bubbles, carefully add the pears. Cook for 6-8 minutes on a medium heat, turning to colour on all sides. Remove from the heat while you prepare the cake batter.
Sift the rye, spelt, baking powder and ginger into a bowl. Any bran left in the sieve should be added to the sifted flour. Set to one side.
In a free standing mixer, cream the butter and sugar until really light and fluffy. Next gradually add the egg, beating between each addition and scraping down the sides of the bowl. Once all the egg has been added, fold in a third of the dry ingredients. Follow with half of the yogurt, then more flour, then yogurt, then finally the flour.
Pour the batter into the prepared cake tin, then arrange the pear slices on the top, adding the caramelised sauce too.
Bake in the centre of the oven for 40-42 minutes or until a cocktail inserted into the centre comes out clean. Cool for 20 minutes and serve slightly warm with cream or yogurt. This cake keeps well for several days.