Begin by preheating the oven to 350 degrees F (175 degrees C). Take two 9-inch cake pans and lightly grease them. If the pans have a bumpy surface, sprinkle them with flour.
In a mixing bowl, combine 3 cups of flour, cocoa powder, baking soda, and salt. Use a whisk to mix everything together.
In another mixing bowl, beat 1/2 cup of butter with an electric mixer until it is smooth and creamy. Add 1 1/2 cups of sugar and continue beating until the mixture is fairly creamy. This should take about 2 minutes. Pour in vegetable oil and beat until combined. Add egg yolks, vanilla extract, vinegar, and enough food coloring to achieve the desired color. Pour in the flour mixture, alternating with buttermilk, on low speed until just incorporated. Be sure not to overmix the batter.
Take a separate bowl and beat the egg whites until they become thick and frothy. Fold them into the batter. Pour the batter into the prepared cake pans.
Place the cake pans in the preheated oven and bake until a toothpick inserted into the center comes out clean. This should take around 30 to 35 minutes, but be careful not to overbake. Allow the cakes to cool in the pans for 10 to 20 minutes before transferring them to a wire rack or serving plate to cool completely.
Combine sugar, flour, and salt in a saucepan. Whisk in milk gradually, making sure there are no lumps. Place the saucepan over medium heat and stir until thickened. Pour the mixture into an airtight container and refrigerate until it is completely cool, approximately 1 hour.
Place the frosting in a mixing bowl and add lemon juice and vanilla extract. Use an electric mixer on high speed to combine. Whip in cream cheese, one tablespoon at a time. Next, whip in butter and continue to mix until you have a really thick frosting. If you're not using it immediately, place it in an airtight container and refrigerate.Frost the cooled cake and place sliced strawberries between the two layers.
