1. Prepare the Cake: Preheat your oven to 350°F (175°C). Grease and flour a 9×13-inch baking dish. Prepare the vanilla cake mix according to the package instructions using 1 cup of water, vegetable oil, and eggs. Pour the batter into the prepared baking dish and bake for 25-30 minutes, or until a toothpick inserted into the center comes out clean. Let the cake cool completely in the pan on a wire rack.

2. Make the Strawberry Sauce: While the cake is cooling, combine the sliced strawberries, sugar, and lemon juice in a bowl. Stir to coat the strawberries evenly and set aside to macerate for about 15 minutes, allowing the strawberries to release their juices.

3. Poke the Cake: Once the cake has cooled, use the end of a wooden spoon or a skewer to poke holes all over the cake, making sure to go deep but not all the way through the cake.

4. Prepare the Jell-O: In a separate bowl, dissolve the strawberry Jell-O mix in 1 cup of boiling water. Stir until the Jell-O is completely dissolved, then allow it to cool for 5-10 minutes. Pour the cooled Jell-O over the poked cake, making sure it seeps into all the holes.

5. Assemble the Cake: After the Jell-O has set for at least 1 hour, spoon the macerated strawberries with their syrup over the top of the cake, covering it evenly.

6. Make the Whipped Topping: In a large mixing bowl, beat the heavy whipping cream, powdered sugar, and vanilla extract on medium-high speed until soft peaks form. Spread the whipped cream over the strawberry layer, covering the entire cake.

7. Serve: Garnish with additional fresh strawberry slices on top. Slice into squares and serve chilled. Enjoy!