Wash, clean and chop the pear into small pieces. Sift the flour and baking powder, beat the eggs with the sugar until whitened.
To the egg mixture add 1 tsp rum or cognac, vanilla and the melted butter, stir and add the flour with baking powder.
Stir in one direction only with a wooden spoon or spatula until the flour is completely absorbed. Set aside 1/2 the prepared cake mixture, add the cocoa to 1, stir until homogeneous.
Oil a cake form, sprinkle with flour and pour in the colorless mixture, pour the cocoa mixture in the middle of it.
With a wooden skewer or stick, smear the cocoa mixture slightly and sprinkle the pear pieces on top. Bake the cake at 338°F (170 °C) to a dry toothpick.