Heat oven to 350°F. Grease a 9-inch round cake pan and line the bottom with parchment.
Whisk 2 cups flour, baking powder, baking soda, and salt in a bowl.
Beat sugar and eggs in a large bowl until pale and slightly thick, about 2 minutes.
Slowly stream in olive oil while whisking until glossy. Stir in orange zest, vanilla, orange juice, and buttermilk.
Fold dry ingredients into the wet mixture just until no dry spots remain.
Toss cranberries with 1 tablespoon flour. Gently fold them into the batter.
Scrape batter into the pan. Sprinkle the top with turbinado sugar.
Bake 42–48 minutes, until a tester comes out clean and the top is golden.
Cool 15 minutes in the pan. Unmold, cool completely, then dust with powdered sugar and slice.