Preheat your oven to 350°F (175°C). Spray a 6-cavity donut pan generously with nonstick cooking spray, making sure to coat the center posts thoroughly.

In a large mixing bowl, whisk together the flour, granulated sugar, baking powder, and salt until no lumps remain and the mixture is evenly combined.

In a separate medium bowl, whisk together the milk, egg, melted butter, and vanilla extract until smooth and fully blended.

Pour the wet ingredients into the dry ingredients and gently fold with a spatula just until the flour disappears. A few small lumps are fine—do not overmix.

Toss the diced strawberries with 1 tablespoon of flour, then gently fold them into the batter, distributing them evenly throughout.

Spoon or pipe the batter into the prepared donut pan, filling each cavity about 2/3 full to allow room for rising.

Bake for 12-14 minutes, until the tops spring back when lightly pressed and a toothpick inserted into the thickest part comes out clean or with just a few moist crumbs.

Let the donuts cool in the pan for 5 minutes, then carefully turn them out onto a wire rack to cool completely, about 20 minutes.

While donuts cool, make the glaze by whisking together the powdered sugar and strawberry puree until smooth. Add milk one teaspoon at a time until the glaze reaches a thick but pourable consistency that coats the back of a spoon.

Dip the top of each completely cooled donut into the glaze, allowing excess to drip back into the bowl. Place glazed donuts on the wire rack and let the glaze set for 10-15 minutes before serving.