Preheat oven to 350°. Line the bottoms of two 8-inch cake pans with parchment rounds.
Combine flour, cocoa, baking powder and salt in a medium bowl.
Beat eggs and sugar in a mixer on high speed until thick and pale, about 5 minutes. Beat in flour mixture. Bring milk and butter to a boil in a medium saucepan. Quickly, but carefully, add milk mixture to flour mixture and beat until smooth; stir in vanilla. Divide mixture evenly among prepared cake pans. Bake 30 minutes, or until pick inserted in center comes out clean. Cool completely on wire racks.
For Frosting, combine butter, marmalade, powdered sugar, and cream in a medium bowl. Beat until well combined. Frost top of one layer of cake, stack another layer and frost top. Frost top and sides of cake with a thin layer of frosting. Chill cake and frosting for 4 hours or overnight. Give remaining frosting a good stir, and use all to frost cake.