Yellow Texas Sheet Cake

Yellow Texas Sheet Cake

1 package. (18.25 ounces) white cake mix
1 Cup buttermilk
1/3 Cup butter, melted
4 egg whites
1/4 teaspoon almond extract

For the frosting:
1 c. chopped pecans
1/2 c. butter
1 c. light brown sugar
1/3 c. buttermilk
2 c. powdered sugar
1/2 tsp. vanilla extract
1/4 tsp. almond extract

To make the cake, beat the cake mix, buttermilk, butter, egg whites and
almond extract together with an electric mixer at low speed for 2 minutes or
until blended. Pour batter into a 15- by 10-inch jelly roll pan.

Bake at 350 degrees for 15 to 20 minutes or until a wooden pick inserted in
center comes out clean. Cool in pan on a wire rack for 2 hours.

To make the frosting, place chopped pecans in a single layer in a shallow
pan. Bake at 350 degrees for 6 minutes or until lightly toasted.

Bring butter and brown sugar to a boil in a 3 1/2-quart saucepan over medium heat, whisking constantly, about 2 minutes. Remove from heat and slowly whisk in buttermilk.

Return mixture to heat and bring to a boil. Pour into bowl of a heavy duty
stand mixer. Gradually add powdered sugar and vanilla and almond extracts,
beating at medium high speed until smooth. Stir in pecans.

Pour immediately over cooled cake in pan and spread quickly to cover cake.

Serves 12.

I am confused. How does white cake mix and no egg yolks produce a yellow cake?