Prepare Strawberry Filling: In a medium saucepan over medium heat, combine fresh strawberries, sugar, and lemon juice. Stir occasionally for about 5-7 minutes until the strawberries soften and release their juices. In a small bowl, mix cornstarch with a tablespoon of water to create a slurry, then add it to the saucepan, stirring continually for about 2 minutes until thickened. Remove from heat and let it cool completely.

Make Lemon Cake Batter: Preheat your oven to 350°F (175°C) and grease two 9-inch round cake pans. In a large mixing bowl, cream together softened unsalted butter and granulated sugar until light and fluffy, about 4-5 minutes. Beat in eggs one at a time, mixing well after each addition. Then, alternate adding the dry ingredients and buttermilk, starting and ending with the dry mixture, until just combined to form the batter.

Bake Cake: Divide the lemon cake batter evenly between the prepared cake pans, smoothing the tops with a spatula. Bake in your preheated oven for 30-35 minutes, or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for about 10 minutes before transferring them to wire racks to cool completely.

Prepare Frosting: While the cakes cool, in a large bowl, beat together softened cream cheese and unsalted butter with an electric mixer until smooth and creamy, about 3-4 minutes. Gradually add the powdered sugar, lemon juice, and lemon zest while mixing on low speed. Continue beating until the frosting is light and fluffy.

Assemble Cake: Once the cake layers are cool, level the tops with a knife if needed. Place one layer on a serving plate and spread a generous amount of strawberry filling on top. Add the second cake layer and frost the entire cake with the lemon cream cheese frosting. Garnish with fresh strawberries, edible flowers, or lemon slices, and refrigerate before serving.