In a large mixing bowl, beat butter and sugar until blended and fluffy.
Add egg and beat until combined and light and fluffy.
Mix in the pumpkin puree and vanilla extract.
Add sifted flour and all dry ingredients. Mix on low speed until blended. Set aside and make the cheesecake mixture.
Cheesecake Ribbon Mixture
In a large mixing bowl, using an electric mixer, add cream cheese and sugar, mix on low-medium speed until no lumps of cream cheese is showing. Add sour cream and egg, mix until smooth.
Assembling
Pour 2/3 of the pumpkin batter into a greased loaf pan. Scoop all of the cheesecake mixture into the pan. Pour remaining 1/3 of the pumpkin batter down the centre of the pan, long side. Use a dining knife to draw crisscross down the loaf to mix the pumpkin batter in the centre to each short sides of the pan. The pumpkin batter is sticky and not as pliable as the cheesecake mixture so go slow and gentle.
Bake at 350 F for 60 minutes until fully baked through when toothpick comes out clean in the middle of the loaf. Cool completely before slicing.