In a large bowl, whisk together the turmeric, cayenne, 1 teaspoon salt and 3 tablespoons vegetable oil. Drop in the cubes of paneer and gently toss. Let the cubes marinate while you get the rest of your ingredients together and prepped.
Thaw the spinach in the microwave in a microwave-safe dish, 5 minutes, then transfer to a clean kitchen towel and squeeze out the excess liquid. Puree in a food processor until smooth. (Alternatively, you can chop it up very finely with your knife.) Set aside.
Place a large nonstick skillet over medium heat and add the paneer as the pan warms. In a couple of minutes, flip the paneer; each piece should be browned on one side. Fry another minute or so and then remove the paneer from the pan to a plate.
Add the remaining 1 1/2 tablespoons vegetable oil to the pan. Add the onion, ginger, garlic, chile and a pinch of salt. Now here?s the important part: Sauté the mixture until it?s evenly toffee-colored, which should take about 15 minutes. Don?t skip this step?this is the foundation of the dish! If you feel like the mixture is drying out and burning, add a couple of tablespoons of water.
Add the coriander, cumin and garam masala. If you haven?t already, sprinkle in a little water to keep the spices from burning. Cook, stirring often, until the raw scent of the spices cooks out and it all smells a bit more melodious, 3 to 5 minutes.
Add the spinach and stir well, incorporating the spiced onion mixture into the spinach. Stir in a little salt and 1/2 cup water. Cook 5 minutes.
Turn off the heat. Stir in the yogurt a little at a time to keep it from curdling. Once the yogurt is well mixed into the spinach, add the paneer. Turn the heat back on, cover and cook until everything is warmed through, about 2 minutes.