01 - Preheat oven to 350°F (175°C). Grease and flour two 8-inch round cake pans and line the bottoms with parchment paper.
02 - In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until evenly distributed.
03 - In a large mixing bowl, beat the softened butter and granulated sugar with an electric mixer until light and fluffy, approximately 3 minutes. Add the eggs one at a time, beating well after each addition. Blend in the lemon zest, lemon juice, and vanilla extract.
04 - Alternately add the flour mixture and buttermilk to the wet ingredients, beginning and ending with the flour. Stir gently until just combined to avoid overmixing.
05 - Gently fold the diced strawberries into the batter using a spatula, taking care not to overmix.
06 - Divide the batter evenly between the two prepared cake pans. Bake for 25–30 minutes, or until a toothpick inserted into the center of each layer comes out clean.
07 - Allow the cakes to cool in their pans for 10 minutes, then invert onto wire racks and let cool completely before frosting.
08 - Beat the softened butter until creamy. Gradually add the sifted powdered sugar, then mix in the lemon juice and strawberry purée. Beat until the frosting is smooth and fluffy. Add a pinch of salt to taste.
09 - Place one cake layer on a serving plate and spread approximately one-third of the frosting evenly across the top. Set the second layer on top and frost the sides and top of the cake. Garnish with lemon zest and fresh strawberry slices if desired.