Begin by preheating your oven to 350°F (175°C). Prepare three 9-inch round cake pans by greasing both the bottoms and sides generously. Line each with parchment paper and set them aside for later.

In a large mixing bowl, whisk together the cake flour, baking powder, baking soda, and salt. Set this dry mixture aside.

Using a stand mixer fitted with the paddle attachment, or a handheld electric mixer, beat the softened butter on medium speed until it achieves a smooth, creamy texture, about 1 minute. Gradually add the sugar, allowing it to blend in slowly. Once all the sugar is incorporated, increase the speed to medium-high and beat for an additional 2 minutes. Add in the vanilla and almond extracts, blending well.

Reduce the mixer speed to medium-low. Add the eggs one at a time, ensuring each is fully mixed before adding the next. Remember to scrape down the sides and bottom of the bowl regularly.

Next, fold in the beaten egg whites in three additions, ensuring each portion is fully mixed in before adding the next.

In a separate bowl or large measuring cup, whisk together the buttermilk, sour cream, and canola oil until they are fully combined.

On low speed, add the dry flour mixture to the batter in three parts, alternating with the buttermilk mixture in two parts. Start and finish with the flour mixture, and avoid overmixing. Blend until just combined.

Divide the batter evenly between your prepared cake pans (about 710 g of batter per pan). Smooth the tops with a spatula. Bake the cakes for 24 to 25 minutes, or until they turn golden around the edges and a toothpick inserted into the center comes out clean.

Once baked, allow the cakes to cool in their pans on a wire rack for 15 minutes. Then, carefully invert the cakes onto cooling racks and leave them to cool completely before frosting.

In the bowl of a stand mixer using the paddle attachment, or a large mixing bowl with a handheld mixer, beat the softened butter on medium-high speed for about 2 minutes, until it becomes completely smooth and creamy.

Turn the mixer to low speed and slowly add the sifted confectioners' sugar, blending until fully incorporated. Add the whole milk, heavy cream, vanilla extract, and salt, and mix until the frosting is smooth and uniform.

Once the ingredients are well combined, increase the mixer speed to high and beat for 1 to 2 minutes, until the frosting becomes light and fluffy. If the consistency is too thick, add a bit more milk. If it's too thin, add a touch more confectioners’ sugar.

To assemble the cake, place one of the cake layers on a serving plate or cake stand. Spread a thick layer of frosting over the top, ensuring it’s even. Place the second cake layer on top and repeat the process. Finish by placing the last cake layer on top and spreading the remaining frosting generously over the entire cake, including the sides.