Add lemon juice and a pinch of salt and continue beating
Slowly add in sugar and beat for 10 minutes or until the batter is glassy and thick and the sugar granules are completely melted. You may need to add a bit more sugar so keep some handy
Add vanilla extract and beat to incorporate completely
Separate the batter for colors and add 3-4 drops of food coloring per batch
Pre heat the oven at 300 F. Pipe the batter onto a baking sheet, in small dollops, leaving about 1" between them.
Bake at 300 F for about 10 minutes then turn the oven to 275 F and continue baking for 20 minutes.
Turn the oven off and keep the cookies in the oven until cool then transfer to an airtight container, stored at room temperature.