1. Preheat oven to 170°C/gas 3. Grease a 20cm-diameter springform cake tin and line the base with baking parchment.
2. Peel, core and quarter the pears.
3. Melt the 25g butter in a frying pan big enough to take all the pear pieces, over a medium high heat. When it's bubbling, add the sugar and stir gently until it has dissolved into the butter. Add the pears and cook gently, turning once or twice, until they have softened and are starting to colour - 5-10 minutes. Set aside to cool.
4. In a mixing bowl, beat the softened butter with the caster sugar until pale and fluffy. Beat in one egg at a time, adding a spoonful of the flour with each to stop the mix curdling.
5. Combine the remaining flour, the ground almonds and the cinnamon, and fold into the mixture. Scrape into the prepared tin. Arrange the pears on top and pour on any buttery juices left in the pan.
6. Bake for about 40-50 minutes or until a skewer inserted into the centre of the cake comes out clean.
7. Stand the cake in its tin on a wire rack to cool for a few minutes, then release the tin. Serve the cake warm with clotted cream - or cold.