Preheat oven to 325°F (160°C). Line the base of a 9-inch springform pan with parchment paper. Grease the parchment paper and the sides of the pan very well with cooking spray. Set aside.
In a large bowl, add the olive oil and eggs. Whisk well to emulsify and incorporate.
Add the milk, orange zest, orange juice, and Grand Marnier. Whisk to incorporate.
Add the granulated sugar and whisk to incorporate.
Add the flour, salt, baking powder, and baking soda. Whisk until just incorporated. Do not overmix. The batter will be on the thin side; this is normal.
Pour the batter into the prepared pan. Place the pan on a baking sheet to catch any potential leaks from the springform pan. Bake for about 70 to 75 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs. Start checking after 60 minutes as oven temperatures vary.
Allow the cake to cool in the springform pan for about 1 hour before carefully releasing the sides. Transfer the cake to a wire rack to finish cooling completely.
Dust with confectioners’ sugar just before serving.
Notes
This cake is best served at room temperature. It can be stored in an airtight container at room temperature for up to 3 days.