Combine orange juice, sugar, and orange zest in a small saucepan over medium low heat. Bring it to a boil and allow it to simmer for 5 minutes.

Add corn starch mixture and stir until sauce thickens. Turn off heat and set aside to allow it to cool.

Lightly grease an 8-in x 4-in loaf pan and line with parchment paper. Preheat oven to 350˚F (180°C).

Sift all-purpose flour, baking powder, and salt into a medium sized bowl.

Cream butter, cream cheese, and sugar in a large bowl until light and fluffy, about 2 minutes.

Beat in eggs, one at a time until combined.

Add orange oil or orange extract. Beat for 30 seconds.

Add half the flour mixture and half of the milk. Beat on low speed. Then add remaining flour mixture and milk. Continue to beat until combine.

Pour half batter into prepared pan. Add half of the orange sauce. Swirl with a butter knife.

Pour in remaining batter followed by orange sauce. Again, swirl with butter knife. Then gently tap the pan on the counter several times.

Place in the oven and bake for 1 hour 10 minutes or until wooden pick inserted in the center comes out clean.

In a large bowl, beat together cream cheese, butter, and orange oil or orange extract until light and fluffy, about 2 minutes.

Gradually beat in powdered sugar until smooth and creamy, another 2 minutes.

Place cake on a cake stand lined with parchment strips on all sides of the cake to keep cake stand clean. Spread frosting onto the cake. Gently pull parchment strips off from underneath the cake.

Decorate with orange slices if desired.