Grease a 9-inch springform pan and line it with parchment paper. Grease the sides with butter.
Cut your pear into thin, 1/4’’ strips, and layer at the bottom of the pan in a circular pattern.
For the crumb topping, in a medium mixing bowl, combine the brown sugar, salt, cinnamon, cardamom, and molasses together until combined. Pour in the butter and mix until smooth. Add the flour, and stir until the mixture becomes lumpy, clumpy, and not completely blended (It's okay to have some flour that is unmixed). Set topping aside.
In stand mixer or large mixing bowl, cream together the butter and sugar until fluffy.
Meanwhile, in a separate bowl, mix together the flour, baking powder, baking soda, salt, cinnamon, and cardamom. Set aside.
Add each egg into the sugar and butter, one at a time. Mix on low and add in the vanilla, molasses, and sour cream.
Finally, beat in the flour mixture on low—don't overmix.
Transfer batter to the prepared pan and smooth the top. Spread the crumbles on top and transfer to the oven.
Bake for 40 to 50 minutes, or until an insert comes out clean from the center of the cake.
Remove the cake from the oven and let it cool in the pan for 10 minutes. Make sure the sides of the pan are not stuck to the cake, then pop the springform open.
Slide onto a dish or cake stand and serve warm with coffee and yogurt, or whipped cream and berries for dessert!