Preheat your oven to 350°F (175°C). This ensures that your donuts bake evenly and rise perfectly.
Lightly grease your donut pan with cooking spray or butter, ensuring that each cavity is well coated to prevent sticking.
In a large mixing bowl, whisk together the all-purpose flour, granulated sugar, baking powder, and salt until well combined.
In another bowl, whisk together the buttermilk, eggs, melted butter, and vanilla extract until smooth.
Pour the wet ingredients into the dry ingredients and gently fold until just combined. Be careful not to overmix; a few lumps are okay.
Using a piping bag or a spoon, evenly distribute the batter into the prepared donut pan, filling each cavity about ¾ full.
Bake in the preheated oven for 10-12 minutes, or until a toothpick inserted into the center comes out clean. The donuts should spring back when lightly touched.
Allow the donuts to cool in the pan for 5 minutes before transferring them to a cooling rack to cool completely.
In a medium bowl, combine the confectioners' sugar, vanilla extract, and milk (or cream). Whisk until smooth and drizzle-able. Adjust the consistency with more milk if necessary.
Once the donuts are completely cool, dip the tops into the glaze and let the excess drip off. If desired, decorate with sprinkles or food coloring.