Preheat Oven to 350˚F. Line the bottoms of two 9" cake pans with parchment paper.: Warmth from a properly preheated oven creates the initial lift in the batter, and lining pans with parchment ensures easy release. As the oven comes to temperature you will smell a faint dry warmth, and the air in the oven will feel steadily hot if you briefly open it. I always preheat for at least 10 minutes so the internal temperature stabilizes, otherwise the cakes may bake unevenly. A common mistake is placing pans in an oven that is still warming, which can cause incorrect rise and texture.
Combine 6 eggs and 1 cup sugar in the bowl of your electric mixer and beat on high speed for 12 minutes or until tripled in volume and fluffy. Whisk together 1 cup flour and 1/2 tsp baking powder then sift it into the beaten eggs in 2 additions, folding it in with a spatula just until all of the flour is incorporated. Add 1/2 tsp vanilla and blend together. Remember that you are relying on the fluffy air-infused batter for the cake to rise. DO NOT OVERMIX or your cake won't rise well. Transfer your batter to your lined cake pans. Set aside.: When you beat the eggs with sugar you will notice the mixture become pale and ribbon like, and when you lift the whisk it should fall back in slow ribbons. This aeration is the structure of the cake, so be patient and let the mixer do the work. Sifting the flour and folding it in preserves that air; look for streaks to disappear rather than constantly stirring. The batter should feel light and airy, not dense, and will pour gently into pans. Avoid the temptation to overwork the batter, as overmixing will deflate it and produce a dense cake. If you see the mix losing volume while folding, stop immediately and bake promptly to capture the trapped air.
Bake at 350˚F for 25-28 minutes or until the top is golden brown and a toothpick comes out clean (poke the side, not the center so your center won't cave) and don't open the oven until 25 minutes have past. Let the cakes cool down on wire racks, then remove from the pans.: As the cakes bake you will watch the tops transform from pale to golden brown and you may hear a faint settling sound as steam escapes. The edges will pull slightly away from the pan, signaling they are nearly done. Using the toothpick on the side ensures the fragile center does not cave in while testing. Resist opening the oven early, since sudden temperature shifts can cause collapse. If the cake looks wet in the center after the time window, give it an additional few minutes while watching closely to avoid overbrowning.
Combine 1 1/2 cups pomegranate juice (POM brand) with 2 Tbsp sugar and stir to combine. Set aside to and stir occasionally until sugar is all dissolved.: The syrup will smell bright and fruity as the pomegranate juice blends with sugar , and stirring helps the crystals dissolve fully. A clear syrup will soak into the crumb evenly, imparting moisture and flavor. If the sugar is not fully dissolved you might end up with a grainy mouthfeel in the soaked layers. Keep stirring and taste a small bit to ensure the sweetness is balanced.
In the bowl of a stand mixer fitted with the whisk attachment, mix the 2 sticks of butter with 3 cups powdered sugar and salt on low speed or until combined (1 min). Increase speed to medium-high and beat until the mixture is pale and fluffy (2 min).: The butter will begin to look whipped and light as tiny air pockets form, and the powdered sugar will lend a cottony texture. The mixture should become noticeably paler and smell sweetly buttery. If it looks greasy, the butter may have been too warm; chill briefly and re whip. A greasy appearance signals you should firm up the mixture before continuing.
Add cream cheese 1-piece at a time and mix until combined. (I waited maybe 3 seconds in between each piece; it's one after another really. Once all of the cream cheese is incorporated, continue to beat 1 more minute.: As you incorporate the cream cheese the frosting will smooth and gain a tangy aroma, and any small lumps should disappear with steady mixing. Work with softened cream cheese to prevent curdling, and scrape the bowl to ensure everything is evenly combined. If you add cold pieces the mixture can seize and become lumpy; warm slightly and beat gently to recover.
Add 4 Tbsp POM juice, 1 Tbsp at a time and mix until combined (1 min). Refrigerate frosting until ready to use.: Adding pomegranate juice gives the frosting a delicate flavor and tint, and adding it in small amounts prevents the frosting from becoming too loose. You will sense a fruity lift in the aroma and a softer mouthfeel when you taste a bit. If the frosting becomes too soft, chill it to firm up before piping; that will restore pipeability and prevent sliding when assembled.
Cut the cake layers in half so you end up with 4 layers. Place the first layer, cut-side-up on your serving platter. Brush 1/4 of the POM/sugar syrup over the first layer. Frost the top. Do this with all 4 layers. You only need a very small amount of frosting on the very top of the cake since you are going to have the pomegranate topping.: When you slice the layers you will expose a fresh crumb that drinks in the syrup quickly, and brushing while the cake is cool helps even absorption. Use a gentle hand so the layers do not tear; a serrated knife in a gentle sawing motion works best. Avoid oversaturating any single layer, as that can make the cake soggy and unstable.
Wipe any excess syrup from the cake platter, then frost the sides. I used my large Wilton 1 M star tip. You want a border that will contain a generous layer of pomegranate topping. Refrigerate your cake for at least 30 minutes before adding the pomegranate topping.: Smoothing the sides creates a tidy surface for the topping to rest on, and the piped border acts like a shallow dam to hold the mixture. When piping you will notice the frosting holds its shape, indicating it is properly chilled and stable. If the frosting is too soft to pipe, return the cake to the fridge for a short time; soft frosting will slump and lose definition.
Place 3/4 cup of POM juice in a small sauce pan, add the 1 tsp vanilla and sprinkle in 2 tsp gelatin, then let stand 1 minute to soften gelatin before putting it on the heat.: This blooming step lets the gelatin hydrate so it dissolves smoothly when warmed. The mixture will smell aromatic from the vanilla , and the surface should look slightly matte after it sits. If you skip blooming, gelatin can clump or fail to set properly, resulting in a topping that never firms.
Wisk in 2 Tbsp sugar and cook over medium heat, stirring, until sugar dissolves and mixture is steaming.: As the mixture warms you will see faint steam and the sugar will vanish into the liquid, leaving a glossy sheen. Stir continuously to prevent localized overheating and scorching. Do not let it reach a rolling boil, as vigorous boiling can break down the gelatin and weaken its setting ability.
Remove from heat and let it cool down a bit (or transfer into a mixing bowl if you don't want to wait) then set the saucepan into a larger bowl of ice water, stirring gently until it is cold and slightly thickened but not set. It doesn't take long so stay with it. Remove from the ice bath.: Cooling gradually keeps the gelatin functional while tempering the mixture so it will set properly once combined with the seeds. You will feel the syrup becoming slipperier and slightly thicker as it cools. If you let it set too far it will be difficult to spoon, so watch closely and stop when it is still pourable but viscous.
Stir in pomegranate seeds and immediately spoon topping onto the chilled cake. Refrigerate your cake until the topping is set (about 1 hour).: The final topping glistens as the seeds catch the light and release a fresh, tart scent. Spoon quickly so the mixture does not begin to set before it is in place. The cake should go into the fridge level to prevent the topping from sliding; a sudden slope will cause the glossy mixture to migrate. If any liquid pools on the platter, gently blot to keep the presentation clean.