01 - Preheat oven to 350°F. Line a 9x13-inch baking pan with parchment paper and lightly grease the sides.
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 minutes.
04 - Beat in eggs one at a time, incorporating each fully before adding the next. Mix in vanilla extract.
05 - Alternately add the flour mixture and milk to the creamed butter mixture, beginning and ending with the dry ingredients. Mix until just combined, being careful not to overmix.
06 - Spread batter evenly in the prepared pan. Bake for 22-25 minutes or until a wooden toothpick inserted into the center comes out clean. Allow the cake to cool completely in the pan on a wire rack.
07 - While the cake cools, combine sliced strawberries, granulated sugar, and lemon juice in a bowl. Toss gently and set aside for at least 20 minutes to allow the berries to macerate and release their juices.
08 - In a chilled bowl, whip the cold heavy cream with powdered sugar and vanilla extract using an electric mixer or whisk until medium-stiff peaks form.
09 - Once the cake is completely cool, spread the whipped cream evenly over the surface. Spoon the macerated strawberries and their accumulated juices generously over the whipped cream layer.
10 - Slice into squares and serve immediately, or refrigerate until ready to serve. For best texture, serve within a few hours of assembly.