Prep the pan and oven: Heat the oven to 350°F (175°C). Lightly oil a 9-inch round cake pan and line the bottom with parchment.
Grease the parchment, too.
Mix the wet ingredients: In a large bowl, whisk 3/4 cup olive oil with 1 cup sugar until glossy. Whisk in 3 large eggs, one at a time, until smooth. Add 1 teaspoon vanilla, the zest of 2 oranges, and 1/2 cup fresh orange juice.
Add dairy: Whisk in 1/2 cup whole milk (or buttermilk) and 1/3 cup Greek yogurt until combined.
Combine dry ingredients: In a separate bowl, whisk 1 3/4 cups all-purpose flour, 1 1/2 teaspoons baking powder, 1/4 teaspoon baking soda, and 1/2 teaspoon fine sea salt.
Bring it together: Fold the dry ingredients into the wet in two additions.
Stir gently until just combined; do not overmix. The batter will be thick but pourable.
Bake: Pour into the prepared pan and smooth the top. Bake 35–42 minutes, until the center springs back and a toothpick comes out with a few moist crumbs.
Cool: Let the cake cool in the pan for 10 minutes.
Invert onto a rack, peel off parchment, and cool completely.
Make the citrus glaze: In a bowl, whisk 1 cup powdered sugar with 2–3 tablespoons fresh orange juice until smooth and pourable. Add 1 teaspoon lemon or lime juice if you want extra tang. For a thinner glaze, add a few drops more juice.
Glaze and finish: Pour the glaze over the cooled cake, letting it drip down the sides.
Zest a little orange on top for aroma and color. Set for 20–30 minutes before slicing.