• Preheat oven to 350 degrees. Line up a donut tray or muffin tray with paper liners, and set aside.
• In a large bowl, combine flour, sugar, salt, baking soda, and baking powder.
• Stir with a fork to combine and make a large well in the center.
• Pour in orange zest, milk, vanilla extract, eggs, and oil into the well and stir until just combined.
• Spoon into prepared tins to be 3/4 full and bake 12 to 15 minutes for donuts. For cupcakes bake for about 18 minutes. Cool completely before frosting.

For buttercream:

• Whip butter, heavy cream, zest, and vanilla together. Slowly stir in powdered sugar until it starts to mix in. Scrape sides and whip for about 30 seconds until light and fluffy. Frost cupcakes and store them inside an airtight container until ready to serve.