In a measuring cup, add the yeast to the warm water then whisk to combine.
Place a large wire mesh strainer over a large bowl then add the flour, sugar and salt. Sift dry ingredients into the large bowl.
In a separate bowl combine the yeast mixture and the milk. Whisk the wet ingredients then combine with the flour mixture, stirring as you pour.
Cover batter with plastic wrap and a towel to keep out the light and let sit overnight on the counter in a cool area.
The next morning the batter will be full of holes and look spongy. Preheat the waffle maker. While it is heating, combine the lemon juice, melted butter, vanilla, baking soda and egg yolks in a medium bowl. Gently fold the the mixture into batter making certain you don't undo all the bubbles that developed overnight. Let rest for 10 minutes to help the batter develop flavor.
In a stand mixer fitted with a whisk attachment, beat the egg whites to soft peaks. Carefully fold the whites into the batter.
Lightly spritz the waffle maker with cooking spray and add the batter, spreading to the edges with a rubber spatula. Shut the lid then cook for approximately 5½ minutes (this varies with each waffle maker) then remove from the machine. Brush away any remaining crumbs left behind with a paper towel, sprits with spray and repeat with the remaining batter.
Enjoy with plenty of butter and pure maple syrup. Yum!