Preheat oven to 400°F. Spray a donut pan with nonstick baking spray or grease it with oil.

In a medium bowl, whisk the flour, baking powder, and salt. Set aside.

In a large bowl, beat the egg with sugar. Add oil, buttermilk, and vanilla. Whisk until combined.

Add the dry ingredients. Mix until just combined.

Fold in the chopped strawberries.

Use a spoon or a piping bag to fill donut cavities with batter 3/4 way full.

Bake for approximately 8-10 minutes or until a toothpick comes out clean. Allow to cool for 10 minutes before flipping the pans upside down over a wire rack.

For the glaze, using a fork, puree the diced strawberries until almost smooth. Add in the vanilla extract and powdered sugar, mix until combined. Add more powdered sugar, if needed, or add milk if the glaze is too thick. 

Drizzle the glaze over the donuts, or dip them into the glaze.