Preheat oven to 350°F. Grease a 9x5-inch loaf pan.

In a large bowl, whisk together egg, pumpkin puree, sugars, pumpkin spice, sour cream, vanilla, cinnamon, and nutmeg until smooth.

In a separate bowl, combine flour, baking powder, baking soda, and salt. Gradually add to the wet ingredients, mixing until just combined.

For the filling, beat cream cheese with sugar and flour until smooth.

Pour about two-thirds of the batter into the prepared loaf pan.

Spread the cream cheese mixture evenly over the batter.

Top with remaining batter, smoothing lightly and pushing into edges.

Bake for approximately 48 minutes until a toothpick inserted comes out clean.

Allow the bread to cool in the pan for 15 minutes, then transfer to a wire rack to cool completely before slicing.

Optionally, serve with butter or cream cheese frosting.