Preheat oven to 350°F Grease and flour 13x9-inch baking pan.
In a large mixing bowl, combine cake mix, water, 3 eggs, oil, and 1/3 cup Eagel Brand. Beat at low speed of electric mixer untl moistened; beat at high speed 2 minutes.
Pour into prepared pan. Bake 40-45 minutes or until a wooden pick inserted in center comes out clean.
In small saucepan over medium heat, combine remaining Eagle Brand, butter and egg yolk. Cook and stir until thickened, about 6 minutes. Add pecans, coconut and vanilla; spread over warm cake. Store covered in refrigerator.