Cake: 2 cups gf flour 1 teaspoon baking powder 1/2 teaspoon baking soda 1/4 teaspoon salt 1-1/2 cups unsalted butter, softened 2 cups sugar 4 eggs 1/2 cup sour cream 1 cup gf vanilla yogurt 1 teaspoon gf vanilla 1-1/2 Tablespoon cinnamon 1/4 cup brown sugar
Frosting: 1 cup granulated sugar 1/3 cup water 1/4 teaspoon cream of tartar dash of salt 2 egg whites 1 teasoon gf vanilla
Cake: Preheat the oven to 350°F. Grease and gf flour the bundt pan. In a large bowl, beat the butter and sugar until light and fluffy. Beat in eggs, sour cream, yogurt and vanilla.
In a separate bowl, combine gf flour, baking powder, and salt. Add dry ingredients to egg mixture and beat on high speed for about 3 minutes.
In a small bowl, combine cinnamon and brown sugar. Set aside.
Pour 1/2 of the batter into the prepared bundt pan. With a spoon make a groove in the center of the batter. Sprinkle cinnamon mixture into the groove. Pour remaining batter into the bundt pan. Bake at 350°F for 50 minutes or until a toothpick inserted in the center comes out clean. Cool 10 minutes in the pan. Remove from pan and cool completely.
Frosting the Cake: In a small saucepan, combine sugar, water, cream of tartar and dash of salt. Bring mixture to a boil, stirring until sugar has completely dissolved. Very slowly, add the sugar syrup to 2 unbeaten egg whites. Beat constantly with an electric mixer until stiff peaks form, about 7 minutes. Beat in 1 teaspoon vanilla. Frost cake and serve.