Delicious donuts made in the waffle maker are the perfect sweet treat ready in under 30 minutes.
In a bowl, whisk together flour, baking soda, and salt.
In a small bowl, whisk together egg, sugar, buttermilk, melted butter, and vanilla. Pour over flour mixture and stir just until smooth. Transfer to a pastry bag.
Brush waffle maker with softened butter. In batches, pipe batter into waffle maker in rings about 1 inch (2.5 cm) thick and 3 inches (7.5 cm) in diameter, spacing rings at least 2 inches (5 cm) apart. Gently close lid (do not squeeze) and cook for about 3 minutes or until golden brown outside and edges no longer look wet. Transfer to a wire rack. Repeat with remaining batter, brushing waffle maker with softened butter as necessary between batches.
Dip or glaze warm or cool doughnuts (see variations), then return to rack. If desired, add sprinkles on top of glaze (if using) and let glaze set.