Preheat the oven to 350 degrees.
Spray or grease and flour a 10-inch tube pan or 13x9-inch baking pan.

1. Prepare the streusel first: In a small bowl whisk together the sugar, flour, cinnamon, cardamom and salt.
2. Cut in the cold butter using a pastry cutter or fork, until the mixture is coarse and sandy. Stir in the pecans, if desired. Set aside.
3. Prepare the cake: Whisk together the flour, baking powder, soda, cardamom and salt. Set aside.
4. In a separate bowl, cream the butter and sugars until light and fluffy.
5. Beat in the eggs, one at a time.
6. Scrape the bowl and add the vanilla and yogurt, mixing until well combined.
7. Add the dry ingredients to the butter mixture with mixer on low speed and blend.
8. Spread half of the batter into the prepared pan.
9. Sprinkle with half of the streusel mixture.
10. Spread the remaining batter on top and sprinkle the remaining streusel evenly over the top of the cake.
11. Bake for 50 to 55 minutes, until the top springs back and a tester inserted in the center comes out clean.
12. Cool on a metal rack.
13. Serve slightly warm or at room temperature.
14. Store tightly covered at room temperature for 3–5 days, or freeze.