Preheat oven to 350°F (175°C). Grease and flour two 8-inch round cake pans, then line the bottoms with parchment paper.

In a medium bowl, whisk together the flour, baking powder, baking soda, and salt. Set aside.

In a large bowl, cream together the softened butter and granulated sugar with an electric mixer until light and fluffy (about 3-5 minutes).

Add eggs one at a time, beating well after each addition. Mix in the vanilla extract.

Gradually add the dry ingredients to the wet ingredients in three additions, alternating with the buttermilk, beginning and ending with the dry ingredients. Mix on low speed until just combined, being careful not to overmix.

Gently fold in the finely diced fresh strawberries.

Divide the batter evenly between the two prepared cake pans. Bake for 28-32 minutes, or until a wooden skewer inserted into the center comes out clean. Do not overbake.

Let the cakes cool in the pans for 10-15 minutes before inverting them onto a wire rack to cool completely. Ensure cakes are completely cool before frosting.

In a small saucepan, combine the diced strawberries, granulated sugar, and lemon juice. Bring to a gentle simmer over medium heat, stirring occasionally.

In a small bowl, whisk together the cornstarch and water to create a slurry. Pour the slurry into the simmering strawberry mixture, stirring constantly.

Continue to cook and stir for 1-2 minutes, until the mixture thickens. Remove from heat and let it cool completely. It will thicken further as it cools. For a smoother filling, you can mash some of the strawberries lightly with a fork.

In a large bowl, beat the softened cream cheese and softened unsalted butter with an electric mixer until smooth and creamy (about 2-3 minutes).

Gradually add the sifted powdered sugar, one cup at a time, mixing on low speed until incorporated, then increasing to medium until smooth. Scrape down the sides of the bowl as needed.

Beat in the vanilla extract. If the frosting is too thick, add milk or cream, one tablespoon at a time, until desired spreading consistency is reached.

Once the cake layers and strawberry filling are completely cool, level the cake layers if necessary using a serrated knife.

Place one cake layer on your serving plate or cake stand. Spread about half of the strawberry filling evenly over the top, leaving a small border around the edge.

Spread a thin layer of cream cheese frosting over the strawberry filling, creating a "dam" to hold the filling in place.

Carefully place the second cake layer on top. Spread the remaining strawberry filling over this layer, again leaving a small border.

Cover the entire cake with the remaining cream cheese frosting, spreading it evenly over the top and sides.

Garnish with fresh strawberry slices or whole strawberries, if desired.

Chill the cake for at least 30 minutes before slicing and serving to allow the frosting to set.