Heat oil in a frying pan or Dutch oven over medium-high heat. After 90 seconds, when the oil is hot, sauté the tofu or seitan for about 7 minutes until golden brown all around. Set aside.
In the same pan, add 2 teaspoons more oil and sauté diced onion for 4 minutes until lightly golden.
Add minced garlic, grated ginger, minced green chilies, turmeric, Kashmiri chili powder, coriander, garam masala, asafetida, and kasuri methi. Cook for a couple of minutes until strongly fragrant, but do not let the garlic darken.
Pour in diced tomatoes and coconut milk. Simmer for 5-8 minutes until the sauce thickens. Add salt to taste.
For a smoother sauce, blend by using an immersion blender. Or blend in batches in a blender and return the blended sauce to the pot.
Gently fold the prepared tofu or seitan into the sauce. Allow it to simmer for a few minutes, letting the sauce penetrate the protein a little.
Serve garnished with cilantro leaves and thinly sliced green chilies. Serve the vegan tikka masala over rice or with your favorite flatbread and Indian pickles.