01 - Preheat oven to 350°F. Grease and line three 8-inch round cake pans with parchment paper.
02 - In a medium bowl, whisk together flour, baking powder, baking soda, and salt until well blended.
03 - In a large bowl, beat butter and sugar until light and fluffy, approximately 3 minutes. Beat in eggs one at a time, then add lemon zest and vanilla extract.
04 - Mix in lemon juice, scraping down sides of bowl as needed to ensure even incorporation.
05 - Add dry ingredients in three additions, alternating with buttermilk, beginning and ending with dry ingredients. Mix just until combined, being careful not to overmix.
06 - Divide batter evenly among prepared pans and smooth tops. Bake for 25 to 30 minutes, or until a toothpick inserted in the center comes out clean.
07 - Cool in pans for 10 minutes, then turn out onto wire racks to cool completely before assembling.
08 - Combine strawberries, sugar, and lemon juice in a saucepan over medium heat. Cook, stirring, until strawberries release their juices, about 5 minutes. Stir in cornstarch slurry and cook until thickened, 1 to 2 minutes. Cool completely.
09 - Beat cream cheese and butter until smooth. Add powdered sugar gradually, then beat in lemon juice, zest, vanilla, and salt until fluffy and well combined.
10 - Place one cake layer on a serving plate. Spread half the strawberry filling over the top, leaving a 1/2-inch border. Top with second cake layer, repeat with remaining filling. Place third layer on top.
11 - Frost the sides and top with lemon cream cheese frosting. Decorate with fresh strawberries, lemon slices, and edible flowers if desired. Refrigerate at least 30 minutes before serving for easier slicing.