Preheat the oven to 170ºC/340ºF and prepare a 3 x 20 cm/8-inch baking pan with parchment paper.

Sift together the all-purpose flour, cornstarch, baking powder, baking soda, and salt.

In a mixing bowl, add granulated sugar and lemon zest, rub together, then add butter and mix on high speed for 3 minutes.

Add eggs two at a time, mixing until combined on low speed.

Mix in half of the dry ingredients, then add sour cream, vegetable oil, lemon juice, and vanilla; mix until just combined. Add the remaining dry ingredients and mix until combined.

Gently fold the batter to ensure all ingredients have combined.

Divide batter into prepared pans and bake for 20-23 minutes until a cake tester comes out clean.

Let the cakes cool on a rack, then remove from the pan and allow to cool completely.

Sift the powdered sugar and freeze dried strawberry powder. Mix the butter in a stand mixer on medium/high speed for 4 minutes, then add sifted sugars in two parts, mixing until incorporated.

Place the first cake layer on your serving dish, spread buttercream, add the next layer and repeat. Cover with a crumb coat and chill for 20 minutes.

Add the remaining buttercream and smooth it out; decorate with fresh strawberries and lemon slices.