Preheat the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans.
In a medium bowl, whisk together the all-purpose flour, baking powder, and salt. Set aside.
In a large bowl, beat the softened unsalted butter and 1 3/4 cups granulated sugar together until light and fluffy, about 3-4 minutes.
Add the eggs one at a time, beating well after each addition. Mix in the vanilla extract.
Alternately add the flour mixture and whole milk to the butter mixture, beginning and ending with the flour mixture. Mix until just combined.
Divide the batter evenly between the prepared cake pans and smooth the tops.
Bake for 28-30 minutes, or until a toothpick inserted into the center comes out clean.
Remove the cakes from the oven and allow them to cool in the pans for 10 minutes, then turn out onto wire racks to cool completely.
To prepare the strawberry filling, combine the chopped fresh strawberries, 1/2 cup granulated sugar, and lemon juice in a medium saucepan over medium heat.
In a small bowl, mix the cornstarch and water until smooth. Add this mixture to the strawberries and cook, stirring constantly, until the mixture thickens and becomes glossy, about 3-5 minutes.
Remove the strawberry filling from heat and let it cool completely before assembling the cake.
Once the cakes are completely cooled, place one cake layer on a serving plate. Spread the strawberry filling evenly over the top.
Place the second cake layer on top of the filling. Optionally, frost the cake with your favorite vanilla buttercream or whipped cream.
Refrigerate the assembled cake for at least 30 minutes before serving to allow the filling to set.