Preheat your oven to 425°F (220°C). Grease a 9-inch round cake pan with butter or cooking spray, then lightly flour it or line with parchment paper.

In a large mixing bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt until well combined. Set aside.

In another bowl, cream together the softened unsalted butter and granulated sugar using a hand mixer or stand mixer on medium speed until light and fluffy, about 3-4 minutes.

With the mixer running, add in the large egg and vanilla extract. Continue mixing until well combined and smooth, about 1-2 minutes.

Gradually alternate adding the dry mixture and buttermilk to the butter mixture, beginning and ending with the dry ingredients, mixing gently until just combined.

Pour the batter into your prepared cake pan, using a spatula to smooth the top evenly. Place the pan in the oven and set a timer for 20 minutes.

Bake for around 20 minutes or until a toothpick inserted in the center comes out clean. Let the cake cool in the pan for 10 minutes.

Transfer the cake to a wire rack to cool completely.

Combine hulled and sliced fresh strawberries with granulated sugar in a bowl. Toss gently and set aside to allow the sugar to draw out their juices.

In a clean mixing bowl, whip heavy whipping cream with powdered sugar and vanilla extract until soft peaks form, about 3-5 minutes.

Once the cake has cooled completely, slice it in half horizontally. Place the bottom layer on a serving platter, spoon half of the sweetened strawberries on top, and add a layer of whipped cream.

Carefully place the second layer of the cake on top, spoon remaining strawberries and juices over it, and finish with a dollop of whipped cream.