In a large mixing bowl, whisk together the flour, sugar, salt, baking soda, and ground cinnamon.
Add the milk, egg, melted butter, and vanilla. Beat until well combined and smooth.
Gently fold in the diced fresh strawberries until evenly distributed.
Spray your donut molds with oil, coating the sides well. Scoop the batter into the molds, filling each about two-thirds full.
Place the pan in the air fryer and cook at 320°F for 10–15 minutes, until golden and a toothpick inserted in the center comes out clean.
Let the donuts cool slightly while you make the glaze.
For the glaze, whisk the powdered sugar with the strawberry puree (or milk) in a small bowl until smooth.
Glaze the slightly warm donuts, then plate, serve, and enjoy.