Orange Glazed Blueberry Doughnuts

(base donut recipe adapted from Wilton)
2 cups cake flour
3/4 cup sugar
2 teaspoons baking powder
1 teaspoon kosher salt
1 teaspoon orange zest
3/4 cup buttermilk, at room temperature
2 eggs lightly beaten, at room temperature
2 Tablespoons unsalted butter, melted
1 teaspoon vanilla extract
1/2 cup blueberries, chopped

3 cups powdered sugar
1/4 cup whole milk
2 Tablespoons freshly squeezed orange juice
2 teaspoons vanilla extract