Begin by preheating your oven to 350°F (175°C). Grease and line a 9-inch round cake pan with parchment paper. This ensures that your sponge cake won’t stick to the pan and makes it easier to remove after baking.

In a large mixing bowl, whisk together the eggs and sugar until the mixture is light and fluffy. You can do this with a hand whisk, but a stand mixer or electric mixer will make the process much faster. Whisk for about 5-7 minutes until the mixture doubles in size and becomes pale yellow.

Next, gently fold in the milk, vegetable oil, and vanilla extract. Stir carefully so as not to deflate the mixture too much. The goal is to incorporate these ingredients without disturbing the air you’ve whipped into the eggs.

Sift the all-purpose flour, baking powder, and salt together into a separate bowl. Gradually fold the dry ingredients into the wet mixture, using a spatula or wooden spoon. Be gentle as you fold to maintain the airiness of the batter.

Pour the batter into the prepared cake pan and smooth the top. Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Once baked, remove the cake from the oven and let it cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely.

While the cake is cooling, prepare the strawberry filling. In a medium saucepan, combine the sliced strawberries, sugar, and lemon juice. Cook over medium heat, stirring occasionally, until the strawberries release their juices and the mixture thickens (about 10 minutes).

If you prefer a thicker consistency, mix cornstarch with a tablespoon of cold water and add it to the strawberry mixture, cooking for another 2 minutes. Let the mixture cool to room temperature.

In a chilled bowl, whip the heavy cream with powdered sugar and vanilla extract until soft peaks form. This will take about 3-4 minutes with an electric mixer. Be careful not to overwhip, as it can turn into butter.

Once the cake has completely cooled, slice it in half horizontally using a serrated knife. Spread a layer of the whipped cream on the bottom layer of the cake, followed by the cooled strawberry filling. Place the top layer of the sponge cake on top and lightly press down.

For the finishing touch, spread a layer of whipped cream on top of the cake. Garnish with fresh strawberry slices for an extra burst of color and flavor. Serve immediately, or refrigerate for a few hours to allow the flavors to meld together.