1. Prepare the Cake:

• Preheat your oven to 325°F (163°C). Grease and line three 8-inch cake pans with parchment paper.
• In a medium bowl, whisk together the cake flour, baking powder, orange zest, salt, and poppy seeds. Set aside.
• In a large bowl, cream the butter and sugar until light and fluffy. Add the egg whites and almond extract, mixing until combined.
• Alternate adding the flour mixture and buttermilk to the butter mixture, beginning and ending with the flour. Gently fold in the sour cream.
• Divide the batter evenly among the prepared pans. Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean. Cool completely before inverting onto wire racks.

2. Make the Almond Buttercream:

• Beat the butter until smooth. Gradually add the sifted powdered sugar, mixing well after each addition. Stir in the vanilla extract, almond extract, and heavy cream. Whip until light and fluffy.

3. Prepare the Orange Curd:

• In a medium saucepan, combine the sugar, orange zest, and orange juice. Cook over medium heat, whisking constantly, then slowly add the eggs and egg yolks. Continue whisking until the mixture thickens.
• Remove from heat and stir in the cold butter until smooth. Strain the curd through a fine-mesh sieve and chill for at least 4 hours.

4. Assemble the Cake:

• Place one cake layer on a serving plate. Spread a layer of almond buttercream, followed by a generous dollop of orange curd. Repeat with the remaining layers.
• Cover the entire cake with almond buttercream, smoothing the edges for a polished look.