1 cup unsalted butter, room temperature
1-1/4 cups sugar
1-1/2 cups flour
1 tsp baking power
1 Tbsp orange zest
1 tsp vanilla
1/4 cup orange juice
1/2 cup orange marmalade
1/3 cup powdered sugar
Bring all cold ingredients to room temperature or the cake will not be light. Preheat oven to 350 degrees. Grease and flour two 9-inch round cake pans.
Beat the butter and sugar together in a large bowl with an electric mixer on med-high speed until fluffy (about 3-5 minutes). Add orange zest and vanilla.
Reduce mixer to medium speed; add eggs one at a time.
Sift the flour and baking powder together. Reduce mixer to low speed. Add the flour in three parts, alternating with the orange juice. Don't over mix.
Spread the mixture evenly into the cake pans. Bake for 25 minutes. Cool completely.
Mix the marmalade with a little water until it's almost pourable, but not too liquidy. Spread over one layer of cake. Top with the other cake layer. Sprinkle powdered sugar on the top by shaking through a sieve. (optional sliced oranges for decoration)