Grease a 24cm-diameter round cake tin.
Peel the pears and slice them into quarters or eighths. Set aside.
Place the sugar and water in a saucepan over low heat until the caramel is made (when it takes color).
Pour over the cake pan and arrange the pears on top of the caramel.
Preheat oven to 350°F
Whisk almond flour, buckwheat flour, corn starch, baking powder, ground cinnamon, and salt in a large bowl.
In a medium bowl beat the eggs with the brown sugar, oil, and vanilla extract until well incorporated. Pour the mixture into the dry ingredients.
Beat until integrate everything, and the mixture is homogeneous (1 minute).
Pour the mixture into the prepared pan over the pears.
Cook for 40 minutes. To know if it´s ready insert a toothpick in the center and when it comes out it should be clean without a trace of batter.
Let cool for 5 minutes and remove from the pan.