Cut the pomegranate in half. De-seed one half and set aside. Juice the other half and set aside.
In a large bowl, whisk the flour, baking powder, and salt together. Set aside.
In another bowl, cream the butter with a hand mixer for about 1-2 minutes on low speed.
Add the sugar and the lemon zest to the butter and beat until creamy and fluffy, about 3 minutes, scraping the bowl frequently.
Then add the vanilla and the eggs, one at a time, beating on medium speed for about a minute after each addition. DO NOT OVERMIX. Scrape the sides of the bowl a few times until everything is well incorporated.
Add the dry ingredients, the lemon juice, and the milk alternately to the butter mixture, beating on high speed until thoroughly combined.
Gently fold half of the pomegranate seeds into the batter (reserve the remaining seeds).
Pour into prepared pan and bake for 45 – 50 minutes, or until an inserted toothpick in the middle comes out clean.
Allow to cool and remove from the pan.