Prepare two 8 inch round cake pans with parchment paper and butter.
Preheat the oven to 375 degrees.
In a large mixing bowl, beat the room temperature butter until pale yellow and thick.
Add in the sugar and eggs and beat again until fully incorperated.
Add in the orange zest and salt and beat, scraping down the sides of the bowl.
Sift flour and baking powder in a bowl and set aside.
Add orange juice to the heavy cream and set that aside.
With the mixer on medium speed, add the flour mixture and heavy cream into the batter, alternating between the two.
Divide batter between the prepared baking pans.
Bake for 25 to 30 minutes, do not overcook.
When you remove, puncture holes all over the top of the cakes and spoon 1/2 cup of rum over each of them. Let them cool before removing.
Meringue Buttercream Frosting
Add the sugar and the egg whites into a heatproof mixing bowl.
Fit the bowl over a pan of simmering water. Whisk constantly until the mixture is hot, sugar is dissolved and the egg whites are a little frothy. Do this for about 4 minutes. It should look like a shiny marshmallow cream.
With the whisk attachment, beat eggs on medium speed until cooled and thicker for about 5 minutes.
Switch to the paddle attachment and one at a time, add in one stick of room temperature butter beating until smooth. Enjoy the deliciousness!