How to Make It
Preheat oven to 350°.
Coat bottom of a 10-inch springform pan with cooking spray; line with parchment or wax paper. Coat bottom and sides with cooking spray; dust with 1 tablespoon flour.
Combine granulated sugar and butter; beat with a mixer at medium speed until well blended (about 5 minutes). Add egg and egg white; beat well.
Lightly spoon flour into dry measuring cups; level with a knife. Combine flour, baking powder, baking soda, and salt in a small bowl; stir well with a whisk. Combine the buttermilk, orange juice, lemon rind, and 1 teaspoon vanilla in a small bowl. Add flour mixture and buttermilk mixture alternately to sugar mixture, beginning and ending with the flour mixture. Fold in 1 1/2 cups blueberries. Spoon batter into prepared pan. Combine turbinado sugar and nutmeg in a small bowl; sprinkle over batter.
Bake at 350° 40 minutes or until a wooden pick inserted in center comes out clean. Cool in pan 10 minutes on wire rack. Remove sides of pan.
Combine sour cream, 1 teaspoon vanilla, and yogurt. Serve cake warm or at room temperature with sour cream mixture and blueberries.