Preheat your oven to 175°C (350°F) and grease your cake pans thoroughly, then line them with parchment paper for easy release

In a medium bowl, whisk together flour, baking powder, baking soda, and salt until evenly combined

In a large mixing bowl, beat softened butter until smooth and creamy

Add sugar gradually and continue beating for 3–5 minutes until the mixture becomes light and fluffy

Add egg whites one at a time, mixing well after each addition to maintain a smooth batter

Stir in vanilla extract and mix until fully incorporated

Add sour cream and mix gently until smooth

Slowly add the dry ingredients in batches, alternating with milk

Mix on low speed and avoid overmixing to keep the cake tender

Add vegetable oil and gently fold it into the batter to enhance moisture

Scrape down the sides of the bowl to ensure everything is evenly combined

Divide the batter evenly between the prepared cake pans

Tap pans lightly on the counter to release air bubbles

Place in the oven and bake for 25–30 minutes or until a toothpick inserted in the center comes out clean

Remove from oven and allow cakes to cool in the pans for 10 minutes

Transfer cakes to a cooling rack and let them cool completely before frosting

To make frosting, beat butter until creamy and smooth

Gradually add powdered sugar while mixing on low speed

Add vanilla extract, salt, and cream

Beat until frosting is fluffy and spreadable

Adjust consistency with more cream if needed

Place one cake layer on a serving plate

Spread an even layer of frosting on top

Add the second layer and frost the top and sides evenly

Smooth or decorate frosting as desired

Let cake rest for 20–30 minutes before slicing