01 - Preheat oven to 350°F. Grease and flour two 8-inch round cake pans, then 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. Mix in the lemon zest, lemon juice, and vanilla extract until incorporated.
04 - Alternately add the flour mixture and buttermilk to the wet ingredients, beginning and ending with the flour. Stir gently until just combined, being careful not to overmix.
05 - Gently fold the diced fresh strawberries into the batter using a spatula, distributing them evenly throughout.
06 - Divide the batter evenly between the two prepared cake pans. Bake for 25 to 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 them cool completely before frosting.
08 - Beat the softened butter until creamy using an electric mixer. Gradually add the sifted powdered sugar, then pour in the lemon juice and strawberry purée. Continue beating until the frosting is smooth and fluffy. Add a pinch of salt to taste.
09 - Place the first cake layer on a serving plate and spread one-third of the frosting evenly across the top. Position the second layer on top, then frost the sides and top of the cake with the remaining frosting. Garnish with lemon zest and fresh strawberry slices if desired.