Preheat your oven to 350°F (175°C). Grease and flour a 9×13-inch baking pan or two 9-inch round cake pans.

In a large mixing bowl, combine the flour, sugar, salt, baking powder, and baking soda. Whisk the dry ingredients together until well mixed.

In another bowl, cream the softened butter using an electric mixer until it's light and fluffy.

Add in the orange juice, eggs, grated orange zest, and vanilla extract. Mix well until fully combined.

Gradually mix the dry ingredients into the wet mixture until just combined. Be careful not to overmix.

Pour the batter evenly into the prepared baking pan(s). Smooth out the top using a spatula.

Bake in the preheated oven for 25-30 minutes for round pans or 35-40 minutes for a rectangular pan, or until a toothpick inserted in the center comes out clean.

Remove from the oven, allow the cake to cool in the pan for about 10 minutes, then transfer it to a wire rack to cool completely.

For the frosting, combine the powdered sugar and fresh orange juice in a bowl. Mix until smooth and spreadable, adjusting the consistency with more orange juice or powdered sugar if necessary.

Once the cake is completely cool, frost the top (and sides if using round pans) with the orange frosting.

Garnish with extra orange zest if desired, then slice and serve.