Special equipment: three 9-inch round cake pans; 5 disposable pastry bags; a wooden skewer
Preheat the oven to 350 degrees F. Butter three 9-inch round cake pans or line them with wax paper or parchment paper and butter the paper.
Divide the Classic Vanilla Cake batter evenly among 5 small bowls. Add food coloring to each bowl--1 drop at a time--until the desired intensity of each color is reached. Scoop each color into a disposable pastry bag and snip the tip of the bag. I tie the ends of the pastry bags with plastic wrap or rubber bands to keep the batter in. Pipe the batter into the first pan, one color at a time, one over the next. (You could also use a spoon, but the pastry bags make this much easier.) Repeat with the remaining 2 pans.
To make the tie dye effect, carefully drag a skewer completely through the batter from the center out to create a pattern with the colors. Don't overmix the colors.
Bake until the middle of the cake feels springy when you gently press your finger against it, 35 to 40 minutes. Set the cakes aside to cool completely before icing.
Level the cakes with a serrated knife. Place one layer on a cake turntable and frost the top with the Vanilla Icing. Add the second cake layer and frost the top. Place the third layer on top and cover the entire cake with a "crumb" coat of vanilla icing. I do a crumb coat--a thin layer of icing spread around the cake to seal in all the crumbs and ensure a neat finish. Unless it's a chocolate cake, the crumb coat is done with vanilla icing. It looks so clean and creates a nice blank canvas for decorating.
Divide the Vanilla Glaze between 2 mixing bowls. Add pink food coloring to one bowl and blue food coloring to the other bowl--1 drop at a time--until the desired intensity of each color is reached. The food coloring will thin out the glaze a bit. You can always add more liquid, but you can't take it away. Working with an offset spatula, spread pink glaze over the top of the cake and let it drip down the sides. Spread the blue glaze over the pink, but do not let it completely cover the pink. Finally, spoon more pink glaze onto the center of the cake top. Alternate the glazes just like you did with the batter. Use a skewer to pull the glaze from the center out to the edge and make the tie dye design. Work quickly before the glaze starts to dry.
With a hand mixer or a stand mixer fitted with the paddle attachment, whip the butter for 1 minute on high speed, then scrape down the sides of the bowl with a spatula. Add the granulated sugar and beat on high speed for 2 minutes. Scrape down the sides of the bowl again. Add the vanilla extract. While mixing at medium-low speed, add the eggs one at a time. Scrape down the edges of the bowl midway through.
Combine the flour, baking powder, and sea salt in a separate bowl. With the mixer on low speed, add half the flour mixture. When it's mostly incorporated, add half the milk. Add the remainder of the dry and wet ingredients, scraping down the sides of the bowl between additions. Stop mixing as soon as you have a smooth batter.
With a hand mixer or a stand mixer fitted with the whisk attachment, whip the butter on high speed for 1 minute. Add the vanilla and whip just to incorporate.
In a separate bowl, mix the confectioners' sugar and salt. With the mixer on low speed, add the sugar mixture 1 cup at a time until completely incorporated. Scrape down the sides of the bowl between additions. Whip on high speed for 3 minutes, until light and fluffy.
With a hand mixer or a stand mixer fitted with the whisk attachment, combine the confectioners' sugar, milk, and vanilla. Mix on low speed until smooth. If the glaze is too thick, add a little more milk to thin it to the desired consistency.
If not using within 10 minutes of mixing, cover the bowl with plastic wrap to keep the glaze from drying out. Store at room temperature.
Alternatively, you can glaze the cake with one color of glaze and top with rainbow sprinkles.
This recipe has been updated and may differ from what was originally published or broadcast.
Adapted from "Cakes by Melissa: Life Is What You Bake It" by Melissa Ben-Ishay © William Morrow Cookbooks 2017. Provided courtesy of Melissa Ben-Ishay. All rights reserved.