We need to dry roast each and every ingredient well. Only then will the sambar powder be very tasty. Here is how I roast them.
First I roast the coriander seeds along with the curry leaves. Roast until the coriander seed turn golden brown and the curry leaves are crispy. It takes about 5-8 minutes. Remove them on to a plate.
Next I roast the dry red chilies for about 5 minutes. The chilies also get crispy. Be careful not to burn them.(Since my family likes everything spicy, I take about 4 cups of chilies, little more than the above given measument.)
After this I add all the chana dal, urad dal, rice and tur dal and roast it together. It pretty much gets roasted in the same time. If you are making a big quantity, this can be roasted one by one. Remove and cool in another plate.
When these are almost roasted, add the rest of the ingredients. Roast for couple of minutes and switch off. Remove the ingredients onto a tray to cool.
Cool all the ingredients well before powdering.
The above measurement yield about 1/4 kg of powder. I prefer to grind it in a flour mill. If your flour mill does not grind small quantities, you can do it in the mixie jar at home.
Once powdered, let it cool in a plate before storing it. If not, water droplets will be formed by condensation which will spoil the powder. You can store it in an air tight container for upto 3-4 months. Use it to make sambar any time.
Ideally for a family of four, 1 tbsp of sambar powder is enough to prepare sambar. Store the remaining in an air tight container.
Adding about 1/4 cup of dry coconut gives a good flavor to the sambar powder but it will not stay fresh for long time. So I usually skip it.