The best vanilla cake

Ingredients:

Cakes

• 3.5 cups premium flour
• 2 tablespoons cornstarch
• 2 tsp baking powder
• 2 teaspoons coarse salt
• 1 teaspoon of baking soda
• 220 g unsalted butter, room temperature
• 2 cups granulated sugar
• 3 tablespoons of vegetable oil
• 1 tbsp vanilla paste or extract
• 3 large eggs, room temperature
• 2 large egg yolks, room temperature
• 2 cups of sour milk or kefir, shake well

Glaze

• 700 g unsalted butter, room temperature
• 4 cups powdered sugar
• 1/3 cup heavy cream
• 1 tbsp vanilla paste or extract
• 0.5 tsp coarse salt

Preparation:

1. Cakes:
   
   Position a rack in the middle of the oven and preheat the oven to 350°F (175°C). Lightly spray two 9-inch (22-cm) cake pans with nonstick spray. Line the bottoms with circles of parchment paper; lightly spray the paper with cooking spray.
2. In a large bowl, whisk together the flour, cornstarch, baking powder, salt, and baking soda until evenly combined. Beat the butter, sugar, and vanilla with a mixer on medium speed until light and fluffy, about 3-4 minutes. Add the eggs and yolks one at a time, mixing after each addition and scraping down the sides of the bowl occasionally.
3. Then, with the mixer on low speed, add the flour mixture in 3 additions, alternating it with the sour milk, beginning and ending with the flour mixture.
   
   
   When measuring flour, spoon it into a dry measuring cup and remove any excess. Scooping flour directly from the bag with a measuring cup will compact it, resulting in dry baked goods.
4. Divide the batter evenly among the prepared pans. Smooth the surface. Bake, rotating the pans halfway through baking, until the cakes are golden brown and a tester inserted into the center comes out clean, 35-45 minutes.
5. Transfer the pans to a wire rack and let cool for 30 minutes. Run a knife between the sides of the pans and the cakes to loosen them, then invert them onto a wire rack. Remove the parchment paper and let the cakes cool completely.
6. Glaze:
   
   In a medium bowl, beat the butter with a mixer on high speed until smooth, about 1 minute. Reduce the speed to low and gradually beat in the powdered sugar. With the mixer running, pour the heavy cream into the bowl, add the vanilla, and salt. Increase the speed to high and beat until the icing is light and fluffy, about 2 minutes.
7. Assembling the cake:
   
   Place one cake layer, domed side down, on a serving plate. Spread 1.5 cups of frosting on top and spread evenly. Place the second cake layer, domed side up, on top. Spread 1.5 cups of frosting. Spread another 1.5 cups of frosting on the sides of the cake and smooth it out completely to create an even, thin layer. It's okay if you can see the cake layers through the frosting; this is just the base layer. Refrigerate for 30 minutes to set the frosting.
8. Spread the remaining frosting over the top and sides of the cake and smooth it out.