Heat oven to 325 degrees F. Grease two 9 x 2-inch round layer-cake pans. Line the bottoms with waxed paper; grease paper; dust the pans with flour.

Prepare Basic White Cake: Mix flour, baking powder and salt on waxed paper. With mixer on medium, beat butter and sugar in bowl until light and fluffy. Add whites, one at a time, beating after each. Beat in vanilla. On low, beat flour mixture alternately with water into butter mixture, beating after each addition. Pour batter into prepared pans.

Bake in 325 degrees F oven for 35 minutes. Unmold and cool, following recipe directions.

When cakes are almost completely cooled, prepare Butter Cream Frosting: Beat together butter, milk, vanilla, salt and 1 cup sugar in medium-sized bowl until smooth and creamy. Gradually beat in remaining sugar until good spreading consistency.

When cakes are completely cooled, slice off rounded top if necessary to flatten (reserve trimmings for snacks). Invert one cake layer onto serving platter. Spread 1/2 to 3/4 cup of frosting over top of cake layer. Place second cake layer on top of first, bottom up. Spread the remaining frosting over sides and top of cake, using long, thin metal spatula to smooth as evenly as possible.

Make Caramel-Drizzle Topping: Heat together the sugar and cold water in a heavy medium-size skillet over medium-high heat, stirring occasionally with a wooden spoon, until the sugar is completely dissolved and the mixture is turned light golden in color, for about 5 minutes; watch carefully so that the sugar mixture doesn't scorch and blacken. Remove the skillet from heat. Using a wooden spoon, quickly drizzle the caramelized sugar mixture over the top of the cake in a zigzag pattern, drizzling back and forth. Let stand to harden.