Preheat Oven & Prepare Pan: Preheat your oven to 356°F (180°C) fan-forced. Grease and line a 9-inch round springform pan with parchment paper. If using a non-stick pan, line the base with parchment paper and grease and dust the sides with flour. Set aside.
Mix Dry Ingredients: In a medium-size mixing bowl, sift together the flour, baking powder and baking soda. Whisk through the salt. Set aside.
Rub Zest Into Sugar: In a separate large mixing bowl, add the sugar and the orange zest. Use your fingers to rub the zest into the sugar for 1 minute until the mixture smells fragrant and resembles damp sand.
Beat Eggs Into Sugar: Add the eggs to the sugar mixture and beat using electric hand beaters or a stand mixer on medium speed for 1 minute until pale and slightly thickened.
Add Olive Oil: With the mixer running on low, slowly drizzle in the olive oil to emulsify, taking about 1 minute and 30 seconds seconds in total. Scrape down the sides of the bowl.
Milk, Juice & Vanilla: Pour in the milk, orange juice and the vanilla. Beat on low for 15 seconds until well combined.
Add Dry Ingredients: Add half of the sifted flour ingredients and beat on low speed until just combined. Add the remaining flour and beat until incorporated, being careful not to overmix, about 10-15 seconds. Use a spatula to gently fold in any extra flour from the sides of the bowl. The batter will be thin.
Transfer Batter: Pour the batter into the prepared pan and smooth the top.
Bake: Bake for 40–45 minutes or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Cool: Let the cake cool in the pan for 15 minutes then transfer to a wire rack to cool completely.
Serve: Dust with powdered sugar before serving or enjoy plain with a dollop of cream or Greek yogurt.