Preheat oven to 350°. Grease and flour three cake pans. Sift together flour and baking powder.
In a mixing bowl, beat butter and sugar together on medium-high speed until fluffy and light, about 3-5 minutes. Add orange zest and vanilla and beat in 15 seconds more.
With mixer at medium speed, add one egg at a time, letting each egg incorporate before adding the next.
Turn mixer to medium-low. Add flour in three parts, alternating with the orange juice until smooth. Don't overbeat.
Spoon equal parts of batter into the three cake pans. Bake for about 25 minutes. Remove cakes and cool completely.
Mix the marmalade with a little water and stir till almost pourable. Spread half the marmalade over one of the layers. Add the next layer on top and spread with the other half of the marmalade. Top with the last layer.
Sprinkle the cake with powdered sugar through a sieve and serve.