Preheat the oven to 350°F (175°C). Grease two 9-inch round cake pans and line the bottoms with parchment paper.
In a large mixing bowl, beat the butter, oil, and sugar until light and fluffy.
Add the egg yolks one at a time, mixing well after each addition.
Add the whole eggs and vanilla extract, continuing to mix until fully incorporated.
In a separate bowl, whisk together the flour, salt, and baking powder.
Gradually add the dry ingredients to the wet ingredients, alternating with the orange juice. Mix until just combined.
Divide the batter evenly between the prepared pans and smooth the tops.
Bake for 25-28 minutes, or until a toothpick inserted in the center comes out clean.
Remove the cakes from the oven, cover immediately with plastic wrap, and place in the refrigerator to cool completely.