Preheat the oven at 170ºC/ 340ºF conventional oven and prepare a 3x20 cm (8 inch) baking pan with parchment paper.
Sift together the all-purpose flour, cornstarch, baking powder, baking soda and salt and set it aside.
260 g all-purpose flour, 1 tablespoon cornstarch, ½ teaspoon baking powder, ½ teaspoon baking soda, ½ teaspoon salt
In a large bowl using an electric hand mixer or in a bowl of a stand mixer, add the butter and granulated sugar and mix it on high speed for 3 minutes.
135 g butter, 225 g granulated sugar
Add the eggs one at a time into the mixture and mix it in until combined.
3 large eggs
Scrape down the sides of the bowl and continue by adding the flour mixture, continuing on low speed, mixing until just combined.
Finally add the sour cream, vegetable oil, vanilla extract and vanilla bean paste and mix until just combined, make sure not to over mix the cake batter.
180 g sour cream, 45 g vegetable oil, 1 teaspoon vanilla extract, 1 ½ teaspoon vanilla bean paste
Using a rubber spatula, give the batter a gentle fold to make sure all of the ingredients have combined.
Divide the cake into the 3 prepared baking pans and with an off set spatula or spoon, even out the cake batter into an even layer. Bake for 13-15 minutes or until a cake tester comes out clean. Be aware that these cake layers stay very light in color and therefore won’t look browned when done.
Let the cakes cool on a cooling rack. After 5 minutes, gently remove the cake from the cake tin and let the cakes cool down completely.