Mix besan, turmeric with yogurt until smooth, this should be lump free. Add 2 cups of water slowly and mix well.
Heat the oil in a saucepan. Test the heat by adding one cumin seed to the oil. If the cumin seeds crack right away, the oil is ready. Add cumin seeds and asafetida.
When the cumin seeds crack, turn off the heat and add fenugreek seeds, and whole red chili. Stir for a few seconds, add red chili powder. Add spinach and stir for a minute.
Add the yogurt mixture and turn the heat to medium. Keep stirring until the kadhi comes to a boil.
Add salt. Turn the heat to medium low. Let the kadhi cook for about 20-35 minutes, stir occasionally. If needed to adjust thickness, add more water. Kadhi should be a pourable consistency.
