Preheat the oven to 350°F (175°C). Grease a 9-inch round cake pan and line the bottom with parchment paper.
Prepare the dry ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon. Set aside.
Cream the butter and sugar: In a large bowl, beat the softened butter and granulated sugar until light and fluffy. This should take about 3-4 minutes.
Add the eggs and vanilla: Beat in the eggs one at a time, ensuring each is fully incorporated before adding the next. Mix in the vanilla extract.
Combine wet and dry ingredients: Gradually add the dry ingredients to the wet mixture, alternating with the sour cream. Begin and end with the dry ingredients, mixing just until combined.
Transfer the batter to the prepared cake pan, smoothing the top with a spatula.
Arrange the pear slices: Lay the pear slices on top of the batter in a circular pattern, slightly overlapping each slice for a decorative effect. Mix the sugar and cinnamon in a small bowl and sprinkle over the top of the cake.
Bake in the preheated oven for 40-45 minutes, or until a toothpick inserted into the center of the cake comes out clean.
Cool the cake: Allow the cake to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely.