Preheat oven to 350 degrees (F). Spray your donut mold with non-stick spray and set aside.
In a medium-sized bowl whisk together the flour, light brown sugar, salt, baking powder, and poppy seeds
In a separate bowl mix the wet ingredients together. Gently fold the wet ingredients into the dry ingredients.
Spoon the batter into the donut pan. Bake the donuts into the pre-heated oven and bake for 15-17 minutes or until they spring back when lightly pressed.
Remove from oven and allow to cool in the pan for 10 minutes and then remove from pan and allow to cool completely before glazing.
For Glaze:
In a small saucepan, heat lemon juice and butter until butter is melted.
In a small bowl whisk together the egg yolks, sugar, and cornstarch until well combined and pale yellow.
Add a small amount of the hot lemon mixture to the egg mixture, whisking constantly.
Add the egg mixture to the remaining lemon mixture in the saucepan and whisk to combine. Cook over medium heat until thickened, stirring constantly, about 3 minutes.
Pour the lemon curd in a small bowl and let cool for 5 minutes.
Whisk in the powdered sugar and heavy cream until smooth. Add more heavy cream if the glaze is too thick.