Preheat the oven to 350F. Toast the hazelnuts in the preheating oven for about 10 minutes.
Grease a loaf pan.
In a small bowl whisk the flour, baking soda, cardamom and salt. Once the hazelnuts are toasted, cooled and crushed, mix them into the flour mixture.
In another bowl mix the mashed pear, sour cream and vanilla.
In the bowl of a stand mixer fitted with the paddle attachment, beat the butter on medium until creamy. Add both sugars and beat on medium until light and fluffy.
Scrape down the bowl and add the two eggs. Mix on medium until combined.
Add the flour mixture and mix on low until incorporated. Add the pear mixture and mix on low until combined.
Scrape down bowl and mix with a spatula to make sure everything is evenly distributed.
Pour batter into prepared pan and bake 45 - 55 minutes. (I definitely needed a longer cook time, but ovens are different so start checking at 45 minutes.)
Let cool on a wire rack for about 20 minutes.