Preheat heat the oven to 350 degrees F. Grease and flour a loaf pan.
Combine the flour, sugar, baking powder, baking soda, and salt together in a large bowl.
Zest the orange and squeeze the zest from the orange. Put the juice in a one-cup measuring cup. Add enough boiling water to make a full cup.
Add the orange zest, vanilla, and butter to the orange juice mixture.
Add the orange juice mixture to the dry ingredients and mix until combined.
Spread the batter into the prepared loaf pan.
Place in the preheated oven and bake for 45 minutes or until a wooden pick inserted comes out clean.
Cool in the pan for about 5 minutes. Then remove from the pan and cool on a cooling rack until completely cooled.