Preheat oven to 425 degrees and grease a 6-count donut pan well with baking spray (the recipe will make about 8 donuts). Set aside.
In a bowl, mix flour, sugar, baking powder, nutmeg, and salt together. Make a well in the center of the dry ingredients and pour in the buttermilk, egg, and vanilla extract. Mix until combined.
Add in butter (or oil) and mix until combined.
At this point, you can mix in the strawberries and divide the batter between the donut cavities, or you can divide the donut batter between the cavities and press the strawberry pieces by hand into the batter (as seen in the video—basically, placing the strawberries in by hand evenly disperses them in the donuts).
Bake for 9-10 minutes, or until the tops of the donuts spring back when touched.
Allow to cool for a few minutes before removing them from the donut pan, then allow them to finish cooling on a wire cooling rack.
Whisk powdered sugar, lemon zest and 2 Tbsp of lemon juice together. If the glaze is too thick, add in the remaining Tbsp of lemon juice.
Dunk each donut in the glaze, and allow to harden. If desired, sprinkle on extra chopped strawberries before the glaze fully hardens.
Enjoy!