Blend the spinach, garlic, ginger, chili pepper and tomatoes with a little water into a smooth puree and keep aside.
Blend the cashews separately with little water to make cashew cream.
In a large pan, add oil and heat on medium.
Add the spices and asofetida and cook for 1 minute.
Add in the spinach puree, salt and sugar and mix well.
Add in the chopped tempeh pieces and cook on low heat for 20-25 minutes until the spinach curry thickens and starts to leave the edges.
Add in the cashew cream and water for desired curry consistency. Taste and adjust salt and spices.
Cook for another 6-7 minutes on medium low till the curry comes to a boil.
Serve hot with with Indian flat breads like Rotis or naans, some sliced tomato salad and pickles! Other variations: Use 1 cup spinach and 1 cup mustard or collard greens!.