To prepare the jar. Dissolve salt in the boiling water. Pour in the glass jar you will be using to ferment the lemons. Let it cool.
Wash the lemons well with cold water. Combine lemons and water in a pot. Heat on the stove and turn off just before it comes to a boil, about minutes.
Slice off the ends the lemons. Quarter the lemons, cutting them open but not all the way through.
In a small bowl, combine salt, nigella and safflower. Sprinkle a little of this mix on the insides of each lemon.
Place in the glass jar, cover and leave it at room temperature for 2 weeks.
Refrigerate and use as desired.