01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper and lightly grease with butter or cooking spray.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt until well blended.
03 - In a large bowl, beat softened butter and granulated sugar with an electric mixer until light and fluffy, approximately 3-4 minutes.
04 - Beat in eggs one at a time, ensuring each is fully incorporated before adding the next. Mix in vanilla extract.
05 - Alternately add the dry flour mixture and milk to the butter mixture, beginning and ending with the flour. Mix gently until just combined, being careful not to overmix.
06 - Spread batter evenly in the prepared pan. Bake for 22-25 minutes or until a toothpick inserted into the center comes out clean. Allow to cool completely in the pan on a wire rack.
07 - While cake cools, combine sliced strawberries, granulated sugar, and lemon juice in a bowl. Toss gently and let stand for at least 20 minutes to macerate, stirring occasionally.
08 - In a chilled bowl, whip heavy cream with an electric mixer until soft peaks form. Add powdered sugar and vanilla, then continue whipping until medium-stiff peaks form.
09 - Once the cake has cooled completely, spread whipped cream evenly over the surface. Arrange macerated strawberries over the cream, distributing them and their juices evenly.
10 - Cut into squares and serve immediately, or refrigerate until ready to serve. For best texture, serve within 2-3 hours of assembly.