Heat oven to 350°F Generously grease bottoms and sides of 2 round pans, 8x1 1/2 or 9x1 1/2 inches, with shortening; lightly flour.
Beat cake mix, water, oil, egg whites and yogurt in large bowl with electric mixer on low speed 30 seconds; beat on medium speed 2 minutes. Pour into pans.
Bake 8-inch rounds 27 to 32 minutes, 9-inch rounds 23 to 28 minutes, or until toothpick inserted in center comes out clean. Cool 10 minutes. Run knife around side of pans to loosen cakes; remove from pans to wire 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.
For greater portability, make the cake as directed using a greased and floured 13x9-inch rectangular pan, and bake 35 to 40 minutes. Cool completely in the pan. Spread frosting over top of cake, and garnish with 1 pint (2 cups) of strawberries.