In a mixing bowl combine 1 cup unsweetened coconut milk and white vinegar. Stir and let it stand for 5 minutes so that it becomes a vegan buttermilk. Now, in the buttermilk add cornstarch, 1 tsp turmeric powder, ¼ tsp chili powder, ½ tsp salt. Stir nicely until all the cornstarch is well dissolved. Add tofu to it and let it marinate for 15 minutes.
Preheat the oven at 375-degree Fahrenheit and prepare a baking sheet with a parchment paper. Spoon out the tofu pieces in the prepared baking sheet. With the spoon drizzle the turmeric buttermilk generously over each piece of tofu and bake it in the middle rack of the oven for 30 minutes. (discard the leftover buttermilk). Once done, turn off the oven and take it out. Keep it aside on a flat surface.
Combine onion, tomato paste, ginger, garlic, 1 ¼ cup coconut milk and cashew nuts in a blender and blend it smooth.
Heat a nonstick pan and pour the blended masala in it. Stir, and cook covered at medium-high flame for 10-15 minutes or until it starts to thicken. (be careful of the splashes).
Add all the spices (cumin powder, coriander powder,¼ tsp turmeric, ½ tsp chili powder, garam masala). Stir nicely and then add salt as per taste. Let it cook uncovered at low flame.
Now, add the tofu pieces to the cooked masala. Scrape cooked buttermilk that sticks on the parchment paper and add it to the curry. Mix gently without breaking tofu. Let it cook for 2 minutes at low-medium flame.
Add remaining ¼ cup coconut milk and stirnicely. Turn it off and garnish with chopped cilantro. Serve with steamedrice/jeera rice.