Preheat oven to 350 degrees F. Generously butter and flour bundt cake pan. Tap out any excess flour. Set aside.
In a large bowl, whisk together flour, baking powder, and salt. Set aside.
In another bowl, combine sugar and orange zest. In the bowl of a stand mixer fitted with a paddle attachment (or using a handheld mixer), cream butter and sugar mixture until smooth. Scrape down bowl as needed.
Add eggs one at a time, ensuring each egg is incorporated before adding the next. Add dry flour mixture in three additions, alternating with the buttermilk. Begin and end with the flour mixture. Mix on low speed until thoroughly combined. Scrape down bowl as needed to ensure thorough mixing.
Pour batter into prepared bundt cake pan. Level batter. Bake for 60-70 minutes until cake springs back to touch and toothpick inserted in cake comes out clean.
Allow cake to cool in pan for 10 minutes. Invert bundt cake onto a wire rack. Remove cake from mold and allow to cool to room temperature.
To make orange glaze: whisk together powdered sugar, vanilla, milk, orange zest, and salt. Whisk until smooth. If glaze is too thick, add another tablespoon of milk. Drizzle over cooled bundt cake.