Preheat your oven to 350°F (177°C) and prepare three 7-inch round cake pans by greasing them with butter or oil and lining the bottoms with parchment paper.

In a mixing bowl, whisk together the cake flour, baking powder, and salt until well blended. Set this mixture aside.

In a stand mixer, combine granulated sugar, unsalted butter, and vegetable oil. Beat on medium speed for 4-5 minutes until pale and fluffy.

Gradually add the egg whites to the creamed mixture, mixing one at a time for about 2 minutes.

Add the sour cream, vanilla extract, and almond extract. Beat until smooth.

Gradually add the flour mixture and milk in alternating batches, mixing only until just combined (about 1-2 minutes).

Divide the batter evenly among the cake pans and bake for 26-30 minutes until a toothpick comes out clean.

Remove the cakes from the oven and let them cool in the pans for about 15 minutes before inverting onto wire racks to cool completely.

In a saucepan, combine the frozen raspberries, granulated sugar, and lemon juice. Cook until raspberries break down (about 5 minutes).

Mix cornstarch with water and stir into the raspberry mixture to thicken, then allow it to cool.

Whip the egg whites, powdered sugar, and salt in a stand mixer until stiff peaks form. Gradually add softened butter, vanilla, and almond extracts.

Level off the cooled cake layers with a serrated knife if needed. Assemble the cake by layering buttercream and raspberry filling between layers.

Chill the assembled cake for about 30 minutes to set the buttercream, then decorate with fresh raspberries and slivered almonds.