Step 1Heat the oven to 325 degrees. Spread the pecans on a dry baking sheet and toast them until lightly browned, 5 to 7 minutes. Coarsely chop, then combine them with the sugar, cinnamon and butter in a small bowl. Set aside.
Step 1Increase the oven temperature to 350 degrees. Grease an 8-inch square baking pan and set aside.
Step 2In the bowl of an electric mixer, cream the sugar and butter until it looks like wet sand.
Step 3In another bowl, stir together the 2 egg yolks and the milk. Set aside.
Step 4Sift the flour with the salt and baking powder and, if using, add the cardamom; set aside.
Step 5On medium speed, alternately add half of the egg mixture and half of the flour to the butter mixture. Scrape down the sides of the bowl and add the rest of the egg mixture and the flour mixture. Beat on medium speed for 2 minutes.
Step 6Whisk the egg whites until they're frothy and form very soft peaks, about 2 minutes. Gently fold them into the batter.
Step 7Pour the batter into the baking pan and smoothe the top. Sprinkle the cake with the topping. Bake until a toothpick inserted in center comes out clean, 30 minutes. Cool in the pan, then cut into pieces and serve.