In a small bowl, whisk together the buttermilk, eggs, vegetable oil and vanilla extract.
3/4 cup (180ml) buttermilk, 2 large eggs, 2 Tbsp vegetable oil, 1 tsp vanilla extract
Add the wet ingredients to the dry mixture and gently stir together until just combined.
Divide the batter into the prepared donut pans, filling almost full.
Bake for 7-9 minutes or until the tops spring back when lightly pressed.
In a small bowl, mix together the sugar and cinnamon.
As soon as the donuts have cooled enough to handle (but still warm), remove from pan and coat in cinnamon-sugar. Set on a wire rack to cool.
1/4 cup (50g) granulated sugar, 1 tsp ground cinnamon
Tip - If you have any trouble with the cinnamon-sugar sticking, lightly brush the donuts with a bit of melted butter and that should help.
Notes
These donuts are best the day of. You can store leftovers in an airtight container at room temperature for 1-2 days. Please note that the cinnamon-sugar melts a bit when stored overnight. Re-coat before serving again.
How to freeze:
Don't coat in sugar mixture and let cool completely. Place in an airtight freezer-friendly container or ziplock bag and store in the freezer for up to 3 months. Defrost overnight in the fridge, warm up in the microwave for 15-30 seconds, then coat in cinnamon-sugar.