Preheat oven to 350°F. Generously butter and flour 10-cup bundt cake pan. Tap out any excess flour. Set aside.
In a large bowl, whisk together flour, baking powder, and salt. Set aside.
In the bowl of a stand mixer fitted with a paddle attachment (or using an electric handheld mixer), cream together butter, sugar, orange zest, orange blossom water, and vanilla until smooth. Scrape down sides of bowl as needed.
Add eggs one at a time, ensuring each egg is incorporated before adding the next. Add sour cream and mix until combined. The batter may look curdled or separated after adding sour cream.
Add dry flour mixture in three additions, alternating with the milk. Begin and end with flour mixture. Mix on low speed until thoroughly combined. Scrape down bowl as needed to ensure thorough mixing.
Transfer 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. Rotate pan midway through baking for even cooking.
Allow cake to cool in pan for 10 minutes. Invert bundt cake onto a wire rack and unmold. Allow cake to cool to room temperature.