Heat oven to 350 degrees F (325 degrees F for dark or nonstick pans). Generously grease and lightly flour bottoms and sides of two 8-inch or 9-inch round pans, or spray with baking spray with flour.
In large bowl, beat cake mix, water, oil, egg whites and yogurt with electric mixer on low speed 30 seconds; beat on medium speed 2 minutes (batter will be lumpy).
Pour into pans.
Bake 8-inch rounds 27 to 32 minutes, 9-inch rounds 25 to 30 minutes, or until toothpick inserted in center comes out clean. Cool 10 minutes. Run knife around sides of pans to loosen cakes; remove from pans to cooling rack. Cool completely, about 1 hour.
Spread 1/3 cup frosting over 1 cake layer to within 1/4 inch of edge.
Cut about 10 strawberries into 1/4-inch slices; arrange on frosted layer. Top with second layer. Frost side and top of cake with remaining frosting.
Cut remaining strawberries in half; arrange on top of cake. Store loosely covered in refrigerator.
