01 - Preheat oven to 350°F. Grease and line three 8-inch round cake pans with parchment paper.
02 - Whisk together flour, baking powder, baking soda, and salt in a bowl. In a separate large bowl, beat butter, sugar, and lemon zest until light and fluffy. Beat in eggs one at a time, then add lemon juice and vanilla. Alternate adding flour mixture and buttermilk, beginning and ending with flour. Mix until just combined.
03 - Divide batter evenly among prepared pans. Bake for 25–30 minutes, or until a toothpick inserted in the center comes out clean. Cool in pans for 10 minutes, then turn out onto wire racks to cool completely.
04 - Combine strawberries, sugar, and lemon juice in a saucepan. Cook over medium heat until strawberries release juices, about 5 minutes. Mix cornstarch and water; stir into strawberries. Cook, stirring constantly, until thickened, 1–2 minutes. Remove from heat and cool completely.
05 - Beat cream cheese and butter until smooth. Gradually add powdered sugar, then lemon juice, zest, vanilla, and salt. Beat until fluffy.
06 - Place one cake layer on a serving plate. Spread half of the strawberry filling over the top, avoiding the edges. Add a layer of frosting to prevent the filling from seeping out. Repeat with the second layer, then top with the final cake layer. Frost the top and sides with remaining lemon cream cheese frosting.
07 - Chill cake for at least 30 minutes before slicing for neat layers.