Preheat the oven to 350°F (175°C). Lightly grease and flour a 9x13-inch baking pan. Line the bottom and sides with parchment paper, leaving a slight overhang for easy removal. Lightly spray the parchment with cooking spray.

In a large mixing bowl, cream the softened butter and granulated sugar using an electric mixer on medium speed until the mixture becomes pale and fluffy, approximately 3–4 minutes. Add the eggs one at a time, beating briefly after each addition. Incorporate the lemon juice and vanilla extract, mixing until combined.

In a separate bowl, whisk together the cake flour, strawberry gelatin, baking soda, and salt. Gradually add the dry ingredients to the creamed mixture in three additions, alternating with the buttermilk (beginning and ending with the dry ingredients). Blend on low speed until just combined.

Gently fold in the diced strawberries using a spatula until evenly distributed throughout the batter.

Transfer the batter to the prepared baking pan, smoothing the top with a spatula. Bake in the preheated oven for 30–35 minutes, or until a toothpick inserted into the center of the cake comes out clean. Allow the cake to cool in the pan on a wire rack for 30 minutes.

Using the parchment paper overhang, carefully lift the cake from the pan and transfer it to a wire rack to cool completely before frosting.

In a mixing bowl, beat the cream cheese with ⅓ cup of the confectioners’ sugar until smooth. Add the diced strawberries and beat briefly until just blended.

In a separate bowl, whip the heavy cream and lemon juice at medium speed until foamy. Increase the mixer speed to medium-high and slowly incorporate the remaining ⅓ cup confectioners’ sugar. Continue whipping until stiff peaks form.

Using a spatula, fold half of the whipped cream mixture into the cream cheese mixture to lighten it. Then gently fold in the remaining whipped cream until fully incorporated and smooth.

Spread the frosting evenly over the cooled cake. For cleaner slices, chill the frosted cake for 30 minutes prior to serving. Slice and serve as desired.