Preheat and prep: Heat your oven to 350°F (175°C).
Lightly grease a donut pan with nonstick spray, making sure to coat the center posts.
Mix dry ingredients: In a medium bowl, whisk 1 1/2 cups flour, 1 1/2 teaspoons baking powder, 1/4 teaspoon salt, and 1/2 teaspoon nutmeg or 1 teaspoon cinnamon.
Mix wet ingredients: In a separate bowl, whisk 1/2 cup sugar, 2 large eggs, 1/2 cup milk, 1/3 cup Greek yogurt or applesauce, 2 tablespoons oil or melted butter, and 1 teaspoon vanilla until smooth.
Combine gently: Add the dry ingredients to the wet and stir just until no dry streaks remain. Do not overmix—a few small lumps are fine.
Fill the pan: Transfer the batter to a piping bag or a zip-top bag with the corner snipped. Pipe the batter into the wells, filling each about 3/4 full.
Bake: Bake for 9–11 minutes, until the donuts spring back lightly when touched and a toothpick comes out clean.
Cool: Let the donuts rest in the pan for 2 minutes, then transfer to a wire rack to cool completely before glazing. They’ll be tender, so handle gently.
Glaze or sugar-coat: For a glaze, whisk 1 cup powdered sugar, 1–2 tablespoons milk, and a splash of vanilla until smooth and pourable.
Dip the cooled donuts, then set on a rack. For cinnamon sugar, mix 1/3 cup sugar with 1 teaspoon cinnamon and toss donuts lightly while still slightly warm.