1. Preheat the oven to 350 degrees. Spray an 8-inch square baking pan generously with cooking spray; set pan aside.

Crumb topping:

1. Place all ingredients except walnuts in the bowl of a food processor. Pulse until the mixture just forms large clumps and holds together when squeezed in the palm of your hand. Pour topping into a mixing bowl and stir in nuts. Press a piece of plastic wrap against the surface of the crumbs and refrigerate until needed, or up to 3 days.

Cake:

1. Toss the cranberries together with 2 teaspoons of flour in a small bowl. Set aside.
2. Whisk together the remaining 2 cups of flour, baking powder, baking soda, salt, cinnamon, and cardamom.
3. Place the sugar and lemon zest in the bowl of a stand mixer and rub the zest into the sugar with your fingertips until the sugar becomes moist and fragrant. Fit the mixer with the paddle attachment and add the butter. Beat on medium speed until light, about 3 minutes. Add the eggs one at a time, beating for 1 minute after each addition. Beat in vanilla. Reduce speed to low and add the flour mixture in 3 parts, alternating with the buttermilk (begin and end with the dry ingredients). Batter will be thick. Gently fold in the berries with a spatula.
4. Pour batter into the prepared baking pan and smooth the top with a spatula. Break crumb mixture into pieces and sprinkle over the cake. The pieces don’t need to be uniform in size—the cake with be cuter if they aren’t. Press the crumbs into the cake lightly with your palm.
5. Bake for 55 to 65 minutes, until crumbs are golden and a cake tester inserted into the center of the cake comes out clean. Transfer cake to a wire rack and cool for 20 to 30 minutes before serving.