Preheat your oven to 350°F (175°C). In a large mixing bowl, combine the boxed cake mix and almond extract. Add in the egg whites and any additional ingredients specified on the cake mix package, then beat with a hand mixer on medium speed for 2 minutes until smooth.

Grease and flour two 9-inch round cake pans. Pour the cake batter evenly into the pans and bake for 30-35 minutes.

Check for doneness by inserting a toothpick into the center; it should come out clean. Let cakes cool in pans for 10 minutes.

After the cakes cool, invert them onto a wire rack to cool completely for about 30 minutes.

In a saucepan, combine flour and milk, stirring constantly over medium heat until thickened, around 3-5 minutes. Let it cool completely.

Once cooled, use a mixer to beat the flour mixture with softened butter and granulated sugar until fluffy and smooth.

Place one cake layer on a serving platter and generously spread a layer of buttercream frosting on top. Add the second cake layer and frost the top and sides of the cake.

Consider adding almond slivers or colorful sprinkles for decoration. Refrigerate if not serving immediately.