• Heat oven to 375°F. Coat 8 x 8 x 2-inch square baking pan with nonstick cooking spray.

  • Melt butter in saucepan. Remove pan from heat. Stir in flour, sugar and cinnamon until mixture becomes coarse crumbs. Measure out and reserve 1/2 cup of the crumbs.

  • Whisk baking soda and sour cream in small bowl. Whisk in vanilla and egg yolk. Stir sour cream mixture into crumb mixture in saucepan, stirring until nearly smooth, with only a few small lumps remaining. Spread batter in prepared pan. Sprinkle top with reserved 1/2 cup crumbs.

  • Bake in 375°F oven 20 minutes or until golden brown and wooden pick inserted in center comes out clean. Serve warm or at room temperature. Or cover and freeze up to 1 month; thaw overnight in refrigerator. Sprinkle with powdered sugar before serving, if desired.

Nutrition Facts

341 calories; 14 g total fat; 9 g saturated fat; 73 mg cholesterol; 140 mg sodium. 51 g carbohydrates; 2 g fiber; 4 g protein;