Preparation:
Preheat the oven.
Whisk together the whole-wheat pastry flour, cinnamon, baking powder, and salt in a bowl. Set aside. Using an electric mixer, beat together the 1/2 cup butter and the sugar on high speed until pale, light, and fluffy. Add the eggs, and beat again until well combined. Using a rubber spatula, fold in the dry ingredients just until combined.
Brush a 9-inch round pan with butter, and dust the pan with a thin, even layer of flour, tapping out the excess. Transfer the batter to the prepared pan and neatly arrange the peat quarters on top, skin side up.
Bake for about 1 hour, or until the top is nicely browned and a toothpick inserted into the middle comes out clean. Let the cake cool for 10 to 15 minutes before removing it from the pan.