Preheat oven to 200°C (400°F).
Peel and core pears while oven is pre-heating.
Cut pears cut into ½”cubes: 3 cups for pear puree. Set aside 3 1/2 cups for the cake. Pear puree: In the bundt pan, add roughly 3 cups, 1 tsp. cinnamon, 1/2 tsp. cardamon, 1 tsp. butter, and place in the pre-heated oven.
Bake for 15 minutes or until soft and tender.
Remove the baked pears from the oven and puree in blender until smooth. This should yield 2/3 - 1 cup pear puree.
Reduce the oven temperature down to 160°C (350°F)
Sift together dry mixture: flour, baking soda, 1 tsp. cinnamon, cardamon, cocoa powder, nutmeg, and salt.
Fold walnuts into dry mixture.
Mix wet mixture: sugar, vanilla sugar, eggs, pear puree, banana, and vegetable oil and mix with handheld mixer.
Fold cubed pears into wet mixture.
Add dry mixture into wet mixture cup by cup and mix with a rubber spatula. Mix until it has a consistent sticky texture and no dry lumps. Grease bundt pan with remaining butter.
Add mixture to bundt pan.
Bake for 55-70 minutes. Check to make sure it is baked through and a knife comes out clean before removing from the oven. (Depending on how juicy the pears are, the consistency can change the baking time). Let bundt pan cool for 10-15 minutes on a wire rack.
Loosen the cake around the edges with a knife to ensure the cake is easily removedfrom the pan and flip over onto a plate.
Garnish with powdered sugar, fresh pears, or whipped cream and enjoy.