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.
03 - In a large bowl, beat butter and sugar until light and fluffy, about 3 minutes. Beat in eggs one at a time, then add lemon zest and vanilla.
04 - Mix in lemon juice, scraping down sides as needed.
05 - Add dry ingredients in three additions, alternating with buttermilk, beginning and ending with dry ingredients. Mix just until combined.
06 - Divide batter evenly among prepared pans. Smooth tops. Bake for 25–30 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.
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, 1–2 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.
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.
12 - Refrigerate at least 30 minutes before serving for easier slicing.