Take a frying pan and heat it on a low flame on your gas stove.
When the pan is hot enough, put 2.5 tbsp or 12 gms of cumin seeds and 1.5 tbsp or 8 gms of black pepper in it. Stir them to dry roast them on a medium to low flame for about two minutes.
When you smell the aroma of the roasted spices, turn the flame of your gas stove off, and transfer the roasted spices onto a plate. Set it aside to cool off completely at room temperature.
Now, take a dry and clean grinder.
When the spices are cool enough, transfer them into the grinder.
Now, it is time to add a few powdered spices to the grinder containing the roasted cumin seeds and black pepper, starting with 4 tbsp or 16 gms of dry mint (pudina) leaves powder.
Then, add 1 tsp or 3 gms of dry ginger powder to the content in the grinder.
Follow it with 1.5 tsp or 7 gms of citric acid.
Now add ¼ tsp or 1 gm of asafetida powder to the grinder.
Then add 2 tbsp or 12 gms of black salt to the content.(Pro tip: Black salt is the foundation of the taste of jaljeera masala powder. So be generous with it). Finally, follow it with 1 tbsp or 6 gms of table salt.
Now, grind the roasted and powdered spices in the grinder into a fine powder.(Pro tip: If you want the masala powder to be coarse, which will not do any harm, grind it once. If you want a finer texture and smoothness in the powder, which will not add to the taste dramatically, grind it a couple of times). Check the powder and when you are satisfied with the texture, transfer it into a bowl and your homemade jaljeera masala powder is ready to be used.