Set a rack in the middle level of the oven and preheat to 350 F (or 176 C) degrees.
Grate the zest from the oranges and place in a large mixing bowl.
Add the eggs to the orange zest and whisk well to mix. Whisk 1 cup of sugar until it lightens, about 1 minute. Whisk in the oil, followed by the milk.
In another bowl, stir the dry ingredients - 1/2 cup of sugar with the flour, baking powder, baking soda, and salt. Whisk the dry mixture into the eggs in 3 separate additions until smooth.
Pour the batter into the bundt cake pan (Don't fill to the brim). There will be a little excess batter, depending on your pan size. (I normally just add it to a cupcake pan and bake)
Bake until it's well risen, with a deep golden color, for about 50 minutes.
Cool the cake on a rack for 5 minutes.
It can stay out for up to 24 hours at room temperature. Cover with saran wrap if leaving out for longer than 24 hours.
Freezes well for up to a month.