Line a lightly greased 15- x 10-inch jellyroll pan with parchment paper; lightly grease parchment paper.
Combine cake flour and next 3 ingredients in a large bowl.
Whisk together eggs and next 5 ingredients in a medium bowl until blended; whisk into dry ingredients just until blended. Pour batter into prepared pan.
Bake at 350° for 30 minutes or until wooden pick inserted in center comes out clean. Cool cake in pan on wire rack 10 minutes. Invert cake onto a wire rack, and remove parchment paper; let cool completely. Transfer cake to a large cutting board.
Cut sheet cake in half to make 2 squares. Place 1 cake layer on a serving plate; spread top with half of Strawberry-Lemon Filling. Top with remaining cake layer. Spread remaining filling over top.
Beat whipping cream and sugar at high speed with an electric mixer until stiff peaks form; spoon into a 1-gallon zip-top plastic freezer bag, press whipped cream into one corner of bag removing excess air, and snip a 1/4-inch hole in corner of bag. Pipe whipped cream vertically onto cake sides.