Prep and Preheat: Preheat your oven to 350°F (175°C). Grease a 10-cavity donut pan (or mini muffin tin for donut holes) generously with nonstick spray or butter. This preparation ensures your donuts will release easily after baking.
Make the Strawberry Donut Batter: In a large bowl, whisk together flour, baking powder, baking soda, salt, sugar, and strawberry powder. In a separate bowl, combine sour cream, buttermilk, egg, melted butter, and vanilla. Whisk until smooth. Pour the wet ingredients into the dry ingredients and stir gently with a spatula until just combined—avoid overmixing to keep the donuts light and fluffy.
Prepare the Cheesecake Swirl: In a small bowl, beat the cream cheese, sugar, sour cream, and vanilla together until smooth and creamy. Transfer the mixture to a piping bag or small resealable bag (snip one corner when ready to pipe).
Assemble the Donuts: Spoon the strawberry batter evenly into the donut pan cavities, filling each about ¾ full. Snip the corner of your cheesecake mixture bag and pipe a small swirl (about 1 teaspoon) into the center of each donut. Use a toothpick or skewer to gently swirl the cheesecake into the batter—just once or twice for a marbled look.
Bake: Bake for 10–12 minutes (or 9–10 for mini donuts) until a toothpick inserted in the center comes out clean or with moist crumbs. Allow donuts to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before glazing.
Make the Strawberry Glaze: In a medium bowl, whisk together powdered sugar, strawberry powder, salt, and 2 tablespoons of milk. Adjust consistency by adding more milk, ½ teaspoon at a time, until the glaze is thick yet pourable.
Glaze the Donuts: Once donuts are completely cool, dip the tops into the glaze, letting the excess drip off. Place back on the wire rack and allow to set for 15–20 minutes before serving.