Topping:

• ½ cup brown sugar
• 1 cup toasted pecans
• 1 ½ teaspoon cinnamon
• ½ cup cake flour
• ½ stick butter, cold, cut in pieces

In a food processor, pulse brown sugar, pecans, cinnamon and cake flour until combined. Add butter in small pieces and pulse until mixture resembles coarse meal. Divide in half and reserve.

Cake:

• 2 ½ cups flour
• 2 ½ teaspoons baking powder
• ½ teaspoon baking soda
• ¼ teaspoon salt
• 2 sticks unsalted butter, room temperature
• 1 ½ cups sugar
• 3 large eggs
• 1 egg yolk
• 2 teaspoons vanilla
• 1 cup sour cream
• Zest of 1 orange
• 1 ½ cups blueberries

Preheat oven to 350 degrees. Butter and flour a 10-inch springform pan. In a large bowl sift together flour, baking powder, baking soda and salt. Set aside. In a large bowl, using an electric mixer, cream butter and sugar until pale and fluffy. Add eggs one at a time, mixing well with each addition. Add yolk and mix well. Add vanilla, sour cream and zest, mix until well incorporated. Slowly add flour mixture, mixing well. Pour half of batter into prepared pan and top with ¾ cup blueberries and half of topping mixture. Spread remaining batter into pan and top with remaining blueberries and topping mixture. Bake for 60-70 minutes until a toothpick, inserted in the middle of the cake, comes out clean. Let cool in pan on a rack for 5-10 minutes before unmolding. Dust with powdered sugar and serve warm.