Preheat the oven to 350°F (175°C). Grease and flour a cake pan.

In a mixing bowl, cream together the softened butter and sugar until light and fluffy.

Add the eggs one at a time, mixing well after each addition.

Stir in the mandarin orange juice and vanilla extract.

In another bowl, whisk together the flour, baking powder, and salt.

Gradually add the dry ingredients to the wet mixture, mixing until just combined.

Pour the batter into the prepared cake pan and smooth the top.

Bake in the preheated oven for 30 minutes or until a toothpick inserted into the center comes out clean.

Allow the cake to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

In a mixing bowl, beat together the softened butter and powdered sugar until smooth.

Add the mandarin orange juice and zest, mixing until well combined.

Spread the frosting over the cooled cake.