Position an oven rack to the mid-oven position and preheat the oven to 350°F. Oil the bottom and sides of a 9-inch round springform pan. A regular 9-inch round cake pan will work too. Line the bottom with parchment and turn it topside up when you remove the cake from the pan to complete cooling.
Whisk flour, baking powder, and salt together in a medium bowl. Set aside. Combine the milk and orange juice. Set aside.
Using a handheld electric mixer, beat the eggs on medium speed until foamy, about 1 minute. Add 1cup of sugar and orange zest, and whip on high speed until the mixture is fluffy and pale yellow, about 2 minutes.
Reduce speed to medium, and while mixer is running, pour the olive oil in a slow, steady stream. Mix until oil is fully incorporated.
On low speed, add half of the flour mixture and mix until barely incorporated. Stop to scrape the sides and bottom of the bowl if needed. Add the milk-orange juice mixture and mix until combined. Add remaining flour mixture and mix until just incorporated. Scrape down the bowl as needed. Be careful to not over mix
Pour the batter into the prepared pan and sprinkle the remaining 1 tablespoon of granulated sugar evenly over the entire surface. Bake until the cake is deep golden brown, about 40 – 45 minutes. Test for doneness by inserting a toothpick in the center of the cake. It should come out with only a few crumbs clinging
Transfer the pan to a wire rack and cool for 15minutes. Remove the sides of the springform pan and cool completely before serving.