Step 1

Position a rack in the lower third of the oven and preheat the oven to 350°F. Spray a 10-inch tube pan with vegetable oil spray and line the bottom with a ring of parchment.

Step 2

To make the streusel: In a small bowl, combine the brown sugar, flour, cinnamon, slat, and pecans, if using. Cut in the butter with a pastry blender until the crumbs are the size of peas. Put the topping in a covered container and set aside in the freezer, while you mix the cake batter.

Step 3

To make the cake: Sift together the flour, baking powder, baking soda, salt, and cardamom; set aside.

Step 4

In the bowl of a stand mixer fitted with the paddle attachment (or in a large mixing bowl, using a handheld mixer), cream the butter and granulated sugar for 4 to 5 minutes, until light and fluffy. Add one egg at a time, mixing well after each addition. Add the vanilla and sour cream and mix just until blended.

Step 5

With the mixer on low, add the flour mixture in thirds to the butter mixture, mixing until just combined and no streaks of flour are visible; scrape down the sides of the bowl as necessary.