Preheat oven to 375 degrees
Coat bunt pan with nonstick cooking spray
Coat pan with granulated sugar
Remove excess sugar from pan
Place sugar and salt in large bowl
Use fingers to rub citrus zest into mixture
Whisk in oil, mascarpone, yogurt, eggs, and vanilla until smooth
Sprinkle baking powder into batter and whisk thoroughly
Sift flour onto batter and use rubber spatula to mix in just until smooth
Pour batter into pan and smooth
Tap pan to get rid of any air bubbles
Bake for 40 minutes - rotate pan at 30 minutes
Cake is done with a toothpick comes out clean
Let rest in pan for 10 minutes before moving to a cooling rack