Preheat oven to 350 degrees.

Grease and flour tube cake pan (or 2 – 9” round cake pans greased on all sides with parchment paper on bottom).

Sift flour, baking powder and salt into a bowl.

In a large bowl, beat butter about 1 minute on medium (til smooth). Add 1 -½ cups sugar and vanilla. Beat till fluffy about 2 more minutes.

Add dry ingredients to butter mixture slowly, about ⅓ at a time alternating with ½ cup of milk at a time.

In a separate bowl, beat egg whites on medium speed til they form soft peaks. Increase speed to high and beat in ¼ cup sugar. Beat til medium firm.

Fold ¼ of egg white mixture in to cake batter to start. Then fold in remainder of egg whites.

Scrape into cake pan(s). Bake 50 minutes for tube pan or 30 minutes for round pans.

Cool 15 minutes then invert tube pan and release cake by running an off set spatula or knife around the side and bottom of the pan. For round pans release edges and invert cakes on to 2 plates. When cool slice the tube pan cake into 2 equal layers.

Combine all ingredients except cream of tartar and berries in a large bowl. Beat 1 minute on low to mix, then increase speed to high and beat another 2-3 minutes .

Add cream of tartar if using when mixture starts to thicken and leave beater tracks. Continue to beat until frosting holds peaks. Do not over-beat.

Position bottom layer on a cake plate and spread a thick layer of frosting over bottom layer. Position top lay on top of frosted bottom layer and frost top and sides. Don't forget to frost the tube hole if you used a tube pan.

Garnish with whole berries. Refrigerate 4 hours or up to 2 days. Cover after 1 hour. Serve with sliced berries on the side.