Place flour, salt, baking powder, and cinnamon in a medium bowl. Whisk to combine. Set aside.
In a mixing bowl, cream the butter and sugar together until light and fluffy.
With mixer on low speed add in the egg and sour cream. Add vanilla and mix on medium speed until blended. Scrape down sides of bowl as needed.
With mixer on low speed add in flour mixture, mix just until blended.
Stir in diced pears.
Pour batter into prepared pan. Batter is thick, use an offset spatula to spread out in pan, making sure to spread batter all the way to edges of pan.
Pour cream cheese filling on top of cake.
Using a knife, slide it under the sliced pear halves and gently place them on top of the cream cheese filling one by one. Make sure to place the thicker end of the pear towards the edge of the pan and the skinnier part towards the center of the pan. NOTE: Pears may slightly sink into cream cheese filling, this is fine.
Sprinkle streusel between the pears and in the center of the cake. NOTE: It's okay if a little of the streusel covers the pears.
Sprinkle top of the cake with cinnamon sugar making sure to coat pears generously.
Place springform pan on a cookie sheet for baking.
Bake 60 min to 65 min. The center should not be jiggly, baked cream cheese filling will bounce back when gently pressed on.
Let cool 30-45 minutes, edges of the cake should release from the sides of the pan as it cools. To be safe run a knife around the edge of the pan before removing the cake from the pan.
Store any leftovers in the refrigerator.