In a medium pot combine the water, sugar, cognac, and vanilla pod. Bring it to a simmer.
Add the pears to a simmering syrup. Cook for 40-50 minutes, until pears are soft.
Remove the pears from the syrup, drain and cool completely.
In a medium bowl mix the flour, cocoa, sugar, salt, baking powder, and baking soda.
In another bowl combine buttermilk, egg, and vegetable oil. Whisk until well mixed.
Pour the buttermilk mixture into the bowl with the flour. Stir with a whisk until smooth.
Preheat the oven to 350 F.
Spray a 9 x 5-inch loaf pan with baking spray. Pour the batter into the pan and arrange the pears bottom side down in line.
Bake for 60 minutes.
Allow sitting for 25 minutes on a cooling rack before removing the cake from the pan.