Preheat oven to 350℉ Line three 6-inch round cake pans with parchment paper. Lightly grease pans and set aside.
Whisk together flour, baking sesame flour, baking powder, baking soda, and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment, beat butter. Add sugar and mix until smooth. Scrape down bowl as needed. Add eggs, vanilla, and black sesame paste. Mix until incorporated. Scrape down bowl as needed.
In three additions, alternate adding dry mixture and milk. Mix on low speed. Scrape down bowl occasionally to ensure all ingredients are fully incorporated.
Divide batter among prepared cake pans. Bake for 30-35 minutes until toothpick inserted in center of cake comes out clean. Allow to cool in pan for 5 minutes before unmolding. Place cake on wire rack and allow to cool to room temperature.