Preheat the oven to 180 °C. Line a deep baking tray (roasting pan) with parchment paper.
Place the softened butter, sugar, and eggs in a large bowl. Beat the mixture with a hand mixer or whisk until smooth and creamy. Add the milk, flour, baking powder, and salt. Mix again until you get a smooth batter with no lumps. Pour the batter into the prepared tray.
Place the sour cream, lemon juice, sugar, and cornstarch in a bowl. Mix well with a whisk or spoon until you get a smooth, homogeneous mixture. Pour the mixture over the batter in the tray and spread it into an even layer.
Cut the strawberries in half and distribute them evenly over the surface of the cake. Bake for 45–50 minutes at 180 °C. Let the cake cool, then slice and serve.