Preheat oven to 350°. Coat a springform size cake pan with nonstick spray. Line with parchment.
Whisk flours, spices, salt, baking soda, and baking powder in a medium bowl.
In a food processor or blender, puree pears lightly until the consistency of mashed bananas.
In a mixer, add pureed pears and sugar. Mix until combined. On medium speed, add eggs on at a time, then oil and vanilla. Finish with sour cream.
On low speed, slowly add dry ingredients and mix, just until combined.
Scrape batter into pan. Bake cake for 15 minutes.
Open oven door. While cake remains in oven, quickly lay pear slices on top. Close oven and continue to bake for another 25-35 minutes or until a toothpick inserted into the center comes out clean. Total bake time should be 55–65 minutes.
Transfer pan to a wire rack and allow to cool for about 20 minutes. Turn out cake onto rack and let cool completely.