Thuvaiyals are Pastes which can be added to rice.
Coconut ThuvaiyalHeat 1 teaspoon oil, add asafoetida, when it bursts add 3 redchillies and 3 teaspoons black gram dhal. When the dhal turns red, add around 1/8th of a coconut and saute lightly. Grind with 1 teaspoon of salt, and water.A tiny bit of tamarind is optional.
Onion ThuvaiyalSame as above. Reduce the chillies to 2 and 1 big onion. Saute till it turns golden brown before grinding into a paste.Tomato can be used instead of blackgram dhal. When doing that, grind the paste and then saute.
Corainder Leaves ThuvaiyalPinch the leaves and wash well. 'Fry asafoetida, 3 red chillies, 3 teaspoon of blackgram dhal in 1 teaspoon of oil. Grind it with the leaves and 1 teaspoon salt. Tamarind too optional. Note the leaves need not be sauted in oil. option 2 Instead of blackgram dhal, 1 tomato can be used and it can be mixed while making vegetables salads with grated carrot or cucumber
Mint Leaves ThuvaiyalSame as Corainder leaves thuvaiyal.
Orange peep Thuvaiyal (Have not tried it)Choose the yellow variety. Scald the peel in 2 teaspoon of oil, with 2 teaspoon black gram dhal,3 red chillies, and asafoetida and grind with 1 teaspoon of salt. If water is not used, can be kept for couple of days.
Dhal Thuvaiyal.In 1 teaspoon of oil, fry half cup red gram dhal and 1 red chilli. Grind this with 1 teaspoon of salt and little coconut if desired.
Other vegetables too can be used to make a Thuvaiyal. Can follow the above principle.
Basically black gram dhal is added as a volumiser. Another volumiser is tomato. Which can be varied depending on tastes preferences. While adding water, while grinding in a mixie add it slowly instead of all at once.Never ever use black gram dhal without turning them red. Raw blackgram dhal tastes awful. :)