01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper and lightly grease with cooking spray or butter.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt until well blended. Set aside.
03 - In a large bowl, beat softened butter and granulated sugar with an electric mixer on medium-high speed until light and fluffy, approximately 3-4 minutes.
04 - Add eggs one at a time, beating well after each addition. Mix in vanilla extract until fully incorporated.
05 - Alternately add the dry ingredient mixture and milk to the butter mixture, beginning and ending with the flour mixture. Mix on low speed until just combined, being careful not to overmix.
06 - Spread batter evenly into the prepared pan. Bake for 22-25 minutes or until a wooden toothpick inserted into the center comes out clean. Cool completely in the pan on a wire rack.
07 - While cake cools, combine sliced strawberries, sugar, and lemon juice in a bowl. Toss gently and let stand for at least 20 minutes, stirring occasionally, until strawberries release their juices.
08 - In a chilled bowl, beat cold heavy cream, powdered sugar, and vanilla extract with an electric mixer on medium-high speed until medium-stiff peaks form.
09 - Once cake has cooled completely, spread whipped cream evenly over the surface. Spoon macerated strawberries and their juices over the whipped cream layer.
10 - Slice into squares and serve immediately. For best results, refrigerate until ready to serve and consume within a few hours of assembly.