Place oven rack in center of oven and preheat to 350º. Coat a 9×5-inch loaf pan with nonstick cooking spray, then sprinkle ½ cup of the Parmesan evenly over the bottom of the pan.

In a large bowl, whisk together the flour, baking powder, cayenne, salt and pepper. Mix in the cheddar using a rubber spatula, breaking up any clumps, until all the cheese is well coated with the flour mixture.

In a medium bowl, whisk together the milk, butter, egg and sour cream. Using a rubber spatula, gently fold the wet ingredients into the dry until just combined, taking care not to overmix. The batter will be heavy and thick. Pour the batter into the prepared loaf pan, smoothing the top with the rubber spatula. Sprinkle the remaining Parmesan evenly over the top of the batter.

Bake until deep golden brown and a toothpick inserted into the center comes out clean, 45-50 minutes. Remember when testing for doneness that a pocket of cheese may look like uncooked batter. Cool in the pan on a wire rack for 5 minutes, then turn out and continue cooling for an additional 45 minutes before cutting.