#1 Preheat oven to 350°F. Grase and flour three 8x2-inch round pans #2 In a medium bowl, whisk together 3 ½ cups of flour, baking powder, and salt. In a separate bowl combine milk and vanilla. Set aside #3 In a large bowl, beat the butter and 1 2/3 cups of sugar until light and fluffy, about 5 minutes #4 Alternating add the flour mixture and milk mixture to the butter mixture. Begin and finish alternating with the flour mixture. Scrape the sides of the bowl as needed #5 In a separate bowl, beat the egg whites and cream of tartar until soft peaks, add 1/3 cup of sugar and continue beating on high speed until medium peaks form. Using a rubber spatula, carefully fold the egg white mixture into the batter #6 Toss the blueberries with 1 teaspoon of flour. Add to batter and incorporate until combined. Evenly distribute the batter among the prepared pans #7 Bake for 25 minutes or until a toothpick inserted in the middle of the cake comes out clean. Remove from the oven and allow the cakes to rest in the pans for 10 minutes. Remove from pans and cool completely #8 While the cakes are baking, prepare the frosting. In a large bowl, beat the butter until smooth. #9 Add the rest of the ingredients and beat at low speed until combined. Increase the speed and beat for 2-3 minutes or until fluffy and smooth. Add more sugar or more cream if needed to achieve the desired consistency. #10 To assemble cake, place the first layer on a serving platter. Scoop approximately 1 ½ cups of the buttercream on the first layer. Spread the buttercream evenly with an off-set spatula #11 Place the next cake layer on top of the iced first layer. Scoop more buttercream onto the second cake layer. Using the same off-set spatula, spread the buttercream evenly over the second layer #12 Lastly, place the third layer on top of the second iced cake layer. Using the remaining buttercream, ice the top and sides of the cake. Decorate with remaining buttercream as desired