Preheat the oven to 350F. Spray a 6 hole regular sized donut pan with some nonstick spray.
In a bowl, whip the egg whites, 2 Tbsp lemon juice, milk, and vanilla. Using a hand mixer or Kitchenaid mixer is best- you want some air whipped into the egg whites.
Once the egg whites have whipped up some, gently fold in the all purpose flour, sugar, baking powder, lemon zest, and 2 Tbsp of the shredded coconut (leave the rest for the topping).
Mix well and divide the batter into the 6 donuts.
Bake in the oven for 14-16 minutes until the donuts are golden brown.
Remove from the oven and let them cool.
Meanwhile, mix the icing sugar with a bit of freshly squeezed lemon juice. You should only need about 1/2 Tbsp of lemon juice. Spread the icing out onto a flat plate and sprinkle the remaining coconut on another flat plate.
Remove the donuts from the pan and lightly press each one into the icing mixture then the coconut. You should have enough to cover all 6 donuts. If you need a little more lemon icing then add a little more to your plate. Be careful not to soak the donuts in it though. It will change the texture and the points.