Place paneer in a bowl and stir in lemon juice and ½ tsp of the salt. Let stand at room temperature while you prepare the rest of the recipe.
Prepare the sauce:
Heat oil in a large pot on medium. Add onion and ½ tsp of the salt. Cook it until it's soft and golden.
Add ginger and garlic. You want them fragrant, which takes about a minute.
Now, add the cumin, garam masala, curry powder, cayenne and turmeric powder. Cook this mixtture for another minute, until fragrant.
Add tomato and cook for another minute. Add water and remaining 1 tsp of salt; bring to a simmer.
Add spinach in batches, letting one handful wilt before adding another. (If using frozen spinach, just put a lid on the pan and wait for it to thaw.)
Carefully transfer this mixture to the blender (or use an immersion blender). Puree until smooth.
Finish the curry
Transfer the sauce back to the pan and bring it to a simmer.
Add the paneer and stir gently to combine. Simmer until paneer is heated through. Add a drizzle of cream, if desired.
**For blanched spinach variation (see notes)
Bring a kettle of water to a boil. Prepare an ice bath by filling a large bowl with ice and cold water.
Place the spinach in a large, heat-proof bowl. Pour boiling water over the spinach and let it stand until the wilted.
Pour into a colander to drain, then immediately scrape into the ice bath.
Once cooled, drain the spinach again, pressing out any excess moisture using a spatula, and discarding ice cubes. Add the drained spinach to the blender with the tomato-spice mixture.
Video
Notes
**Blanched Spinach VariationIf you want your Palak Paneer to have a bright green color (as pictured) and/or less bitterness, you can blanch it and shock it in ice water after wilting it.