Heat oven to 350
Grease a spingform pan with butter. Line the bottom of the pan with parchment.
Whisk flour, sugar, salt, baking powder, and baking soda in a medium bowl.
In a second bowl, whisk butter, milk, olive oil, eggs, Campari, zest and juices.
Fold the dry ingredients into the wet ingredients
Scrape batter into the prepared pan.
Bake around 45 min - 1 hour. You are looking for the top to be golden brown and to spring back when touched. A tester might have a few crumbs.
Let cake cool completely.
Use a butter knife to release from sides.