Preheat oven to 350º. Oil a 9 inch spring form pan and line it with parchment paper.
In a bowl, whisk the flour, sugar, salt, baking powder and baking soda.
In another bowl, whisk the olive oil, milk, eggs, orange zest, juice and Grand Marnier.
Add the dry ingredients and whisk until combined.
Pour the batter into the prepared pan.
Bake for 45 to 50 minutes or until the top is golden and a toothpick comes out clean.
Transfer the cake to a rack and let cool for 30 minutes. Run a knife around the bottom and place on a serving dish.
Let cool completely before serving.
Serve with orange curd and dust with powdered sugar if desired.