Preheat the oven to 350°F. Grease a 9×5-inch loaf pan with floured cooking spray or grease and flour it thoroughly. Set aside.

In a large bowl, combine the egg, pumpkin puree, brown sugar, granulated sugar, coconut oil, sour cream, vanilla extract, cinnamon, pumpkin pie spice, and nutmeg. Whisk these ingredients together until they are well incorporated. Add the flour, baking powder, baking soda, and salt (if using). Gently fold these dry ingredients into the wet mixture using a spatula or stir with a spoon, being careful not to overmix. Set aside.

Pour about two-thirds of the bread batter into the prepared loaf pan. Smooth the surface with a spatula, ensuring the batter reaches the edges and corners.

In another bowl, whisk together the cream cheese, egg, granulated sugar, and flour until smooth and well-combined. You may also use a hand mixer for this step if preferred.

Evenly spread the cream cheese mixture over the bread batter in the pan, gently smoothing the top with a spatula to ensure it reaches the corners and edges.

Pour the remaining pumpkin bread batter over the cream cheese layer. Carefully smooth the top without disturbing the cream cheese filling, ensuring the batter is evenly distributed and reaches the sides of the pan.

Bake for approximately 48 minutes, or until the top of the loaf is golden and domed, and the center is set. To check for doneness, insert a toothpick into the bread portion (not the cream cheese); it should come out mostly clean with a few moist crumbs, but no batter. Note that the cream cheese layer will not fully solidify, so the toothpick test may not be entirely accurate.

Cool the bread in the pan for about 15 minutes. Then, remove the loaf and place it on a wire rack to cool completely before slicing and serving.