Preheat the oven to 350°F (175°C). Lightly grease two 8-inch square baking pans with baking spray. Line the bottom of each pan with parchment paper, spray again, and flour the parchment.
In a medium bowl, whisk together cake flour, baking powder, and salt; set aside.
In a large mixing bowl, beat sugar and butter with an electric mixer at medium speed until light and fluffy, 3-5 minutes. Add vanilla extract. Gradually add the flour mixture alternately with milk, starting and ending with flour.
In a clean mixing bowl, beat egg whites at medium speed until stiff peaks form. Gently fold the egg whites into the batter. Divide batter evenly between prepared pans.
Bake in the preheated oven until a toothpick inserted into the center comes out clean, 30-35 minutes. Cool cakes in pans on a wire rack for 15 minutes. Turn cakes out onto the rack, remove parchment, and cool completely, about 1 hour.
Transfer cakes to a cutting board. Trim the rounded tops to resemble sandwich bread. Slice each cake in half horizontally to create 4 layers.
Beat peanut butter, cream cheese, honey, butter, and salt at medium speed until smooth. Gradually add powdered sugar, 1/2 cup at a time, until smooth. Add milk, 1 tablespoon at a time, until spreadable consistency is reached.
Beat peanut butter, cream cheese, honey, butter, and salt at medium speed until smooth. Gradually add powdered sugar, 1/2 cup at a time, until smooth. Add milk, 1 tablespoon at a time, until spreadable consistency is reached.
Whisk strawberry jelly in a small bowl to loosen.
Place one cake layer on a serving platter. Spread 1/3 of the peanut butter mixture over the cake, followed by 1/3 of the jelly. Repeat with remaining layers, finishing with the final cake layer trimmed side up. Slice diagonally to create a sandwich effect.