Mill the flour: Mill 126 grams hard white wheat berries and 84 grams soft white wheat berries. Whisk the freshly milled flours together to create a balanced flour blend that yields approximately 210 grams (1¾ cups) of flour. If preferred, substitute 1¾ cups all-purpose flour.
Preheat the oven: Preheat to 350°F and grease a 7x9-inch baking pan. A light coating of butter or baking spray helps ensure the cake releases easily after baking.
Whisk the dry ingredients: In a medium bowl, whisk together the flour, baking powder, baking soda, and salt until evenly combined. This helps distribute the leavening ingredients throughout the batter.
Cream the butter and sugar: In a large mixing bowl, beat the softened butter and granulated sugar together for 3–4 minutes, until light and fluffy. The mixture should become noticeably paler in color.
Add the egg yolks and citrus: Mix in the egg yolks until fully incorporated. In a separate bowl, stir together the lemon zest, lemon juice, vanilla, and buttermilk.
Combine the batter: Alternate adding the dry ingredients and buttermilk mixture, beginning and ending with the flour mixture. Mix just until combined to keep the cake tender.
Whip the egg whites: In a clean bowl, beat the egg whites to soft peaks. They should hold a gentle curve when the beaters are lifted.
Fold in the whites: Gently fold the whipped egg whites into the batter until no streaks remain. Take your time to preserve as much air as possible.
Bake: Spread the batter evenly into the prepared pan and bake for 28–35 minutes, until a toothpick inserted into the center comes out clean. Allow the cake to cool completely before frosting.
Make the buttercream: Beat the butter until smooth, then gradually add the powdered sugar, lemon juice, lemon zest, salt, and cream until light, fluffy, and easily spreadable.
Frost and decorate: Spread the buttercream over the cooled cake and arrange the strawberries into a lobster design. Use larger berries for the claws and smaller pieces for the body and tail.
Chill and serve: Refrigerate until ready to serve. A brief chill helps the frosting set and makes cleaner slices.