Prep the strawberries. Core and slice strawberries into 1/4 inch slices, toss gently with 1/4 cup granulated sugar. Cover and refrigerate for 1 hour.
Preheat and prep. Preheat oven to 325 degrees. Grease a 9x13 inch baking dish with cooking spray and set aside.
Mix dry ingredients. In a large bowl, whisk together cake flour, baking powder, salt, and 1 1/4 cups of the sugar until thoroughly combined. Add melted butter, water, vanilla, 2 whole eggs, and 4 egg yolks. Whisk until combined and set aside.
Whip egg whites. In the bowl of a stand mixer fitted with the whisk attachment, beat 4 egg whites on medium-low speed until frothy, 20-30 seconds. Increase speed to medium-high, slowly adding remaining 1/4 cup sugar. Beat until soft peaks form, 1-2 minutes.
Fold and bake. Add 1/3 of the whipped egg whites to the batter and whisk until combined. Add remaining whites and gently fold until no streaks remain. Pour batter into the prepared pan. Bake for 30 minutes or until golden brown and a toothpick inserted in the center comes out clean. Cool on a wire rack for 1 hour.
Make the lemon curd. In a saucepan, whisk sugar and lemon zest until pale yellow and sandy, 20-30 seconds. Add egg yolks and salt, whisk until combined. Slowly whisk in lemon juice. Cook over medium-low heat, stirring constantly, until thickened and coats the back of a spoon, 5-6 minutes. Remove from heat, whisk in chilled butter until smooth. Pour into a bowl, cover with plastic wrap directly on the surface. Refrigerate until ready to use.
Make the whipped cream. Beat softened mascarpone and sugar in a stand mixer at medium-high speed until smooth, 20-30 seconds. Add 1/3 of the heavy cream, mix on medium until smooth, scrape bowl. With mixer on medium-low, slowly add remaining cream. Increase to medium-high and beat until stiff peaks form. Add vanilla and mix until just incorporated.
Assemble. Spread a thin layer of lemon curd over the cooled cake. Top with whipped cream and spread evenly. Arrange sliced strawberries and accumulated juices on top. Cover and chill until ready to serve.