Blueberry Dream Cake

Ingredients

• 1 1/2 cups all-purpose flour
• 1/2 cup granulated sugar
• 1 1/2 teaspoons baking powder
• 1/3 cup butter, softened
• 2 egg whites, lightly beaten
• 1 teaspoon vanilla
• Cake:
• 3 cups fresh blueberries or 3 cups frozen blueberries
• 2 tablespoons all-purpose flour
• 2 cups low-fat plain yogurt
• 1 egg, lightly beaten
• 2/3 cup granulated sugar
• 1 teaspoon vanilla
• 1 lemons or 1 orange, grated rind of