Preheat oven to 180 degrees Celsius

In a bowl, whisk 2 1/2 cups flour with baking powder and salt; set aside.

In a mixing bowl, cream butter and sugars on high speed until light and fluffy. Add eggs, one at a time, beating until incorporated. Beat in vanilla.

Reduce speed to low; add flour mixture in three additions, alternating with two additions of sour cream.

In a bowl, toss blueberries and zest with remaining teaspoon flour; gently fold into batter

Coat a 12-cup nonstick Bundt pan with cooking spray. Spread batter in prepared pan.

Bake cake on bottom rack of oven until a toothpick inserted into center of cake comes out clean, 60 to 70 minutes. Cool in pan 20 minutes.

Invert onto a rack; cool completely, top side up.

For making Passionfruit icing: mixing passionfruit pulp with icing sugar. Ice cake with a hot, clean knife.