Preheat oven to 350°F (175°C) and grease a 9x9 inch square baking pan or line with parchment paper.

In a medium bowl, whisk together flour, baking powder, cardamom, and salt for the cake batter.

In a large mixing bowl, cream softened butter with granulated sugar until light and fluffy, about 3-4 minutes.

Add eggs one at a time, beating well after each addition, then mix in vanilla extract.

Alternately add flour mixture and milk to butter mixture, beginning and ending with flour mixture, mixing just until combined.

Pour batter into prepared baking pan and spread evenly.

For crumb topping, combine flour, brown sugar, cardamom, cinnamon, and salt in a bowl.

Cut in cold butter using pastry cutter or fingers until mixture resembles coarse crumbs.

Sprinkle crumb topping evenly over cake batter.

Bake for 35-40 minutes until toothpick inserted in center comes out clean.

Cool in pan for 10 minutes before serving warm or at room temperature.