Preheat the oven to 170°C/340F. Grease a loaf tin and set it aside. Melt the butter and allow it to cool a bit. Zest one of the oranges using a zesting tool or Microplane. Juice all of the oranges.
3-4 oranges, 75 grams butter
In a large mixing bowl, beat the eggs and sugar until the mixture is light, fluffy and doubled in size. This will take 3 to 5 minutes using an electric hand mixer or stand mixer.
150 grams white granulated sugar, 2 large eggs
With the mixer running on the lowest setting, pour in the melted butter, vanilla, orange juice and milk. Mix until well combined.
75 grams butter, 50 mL orange juice, 60 mL milk, 2 teaspoons vanilla extract
Either whisk together the flour, baking powder and salt and add to the wet ingredients or sift the ingredients over the wet ingredients. Toss in the zest of one of the oranges. Mix until combined.
220 grams plain flour, 2½ teaspoons baking powder, ¼ teaspoon table salt
Pour or spoon the cake batter into the prepared loaf tin. Bake for 35 to 45 minutes or just until a cake tester or toothpick comes out mostly clean. Be careful to not overbake the cake.