1. Preheat oven to 350 degrees. Lightly grease cake pans and line the bottoms with parchment paper.
2. In a large bowl or the bowl of a stand mixer, add the eggs, sugar, oil, and strawberry extract. Begin mixing until combined, scraping down the sides and bottom of the bowl as needed.
3. Combine cornstarch, flour, salt, and baking powder in a separate bowl, and whisk together. Alternate adding the dry ingredients and pouring milk into the egg/sugar ingredients. Mix until well combined, scraping sides midway through. Add the strawberry pie filling and mix no longer than 1 1⁄2 minutes.
3. Pour equal amounts of batter into 2 6-inch round pans. Bake at 350 degrees for approximately 40 mins. Check with a toothpick. It should come out clean. If not, bake an additional 2 mins.
4. Allow cakes to cool on a wire rack for 10 minutes before removing them from the pans and returning them to the wire rack to cool completely.
5. While the cakes are baking, prepare the frosting. Mix the salted butter, powdered sugar, and strawberry extract together until creamy and smooth. Cover and allow to rest while the cakes cool completely.
6. To decorate: Place one of the cakes on a shallow plate. Using the angled spatula, add some of the buttercream to the top of the cake layer. In a back-and-forth motion, spread gently to cover the entire top of the cake.
7. Top this with a layer of fresh strawberries. Place the next cake layer on top of the first (top side down). Press down gently, as this helps remove some of the air pockets that may have developed.
8. Place more buttercream on the cake and gently work back and forth to the edge of the cake. Frost the sides of the cake.
9. Use the angled spatula to smooth out the buttercream as much as possible, or make slight ridges by turning the cake on the turntable.