01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper and lightly grease the interior.
02 - Whisk together flour, baking powder, baking soda, and salt in a medium bowl until thoroughly blended.
03 - Beat softened butter and granulated sugar in a large bowl until light and fluffy. Add eggs one at a time, mixing well after each addition. Incorporate vanilla extract.
04 - Alternate adding the dry flour mixture and milk to the creamed butter mixture, beginning and ending with the flour. Mix only until just incorporated to avoid developing gluten.
05 - Spread batter evenly into the prepared pan. Bake for 22-25 minutes until a toothpick inserted into the center emerges clean. Cool completely in the pan on a wire rack.
06 - Combine sliced strawberries with granulated sugar and lemon juice. Let stand for at least 20 minutes, stirring occasionally, to release natural juices.
07 - Whip cold heavy cream with powdered sugar and vanilla extract in a chilled bowl until medium-stiff peaks form.
08 - Once the cake has cooled completely, spread whipped cream evenly over the surface. Distribute macerated strawberries and their accumulated juices over the cream layer.
09 - Cut into squares and serve immediately, or refrigerate until ready to serve.