Place the lentils into a small saucepan and cover with about 3 inches of water. Place over high heat and bring the water to a boil. Allow to cook until the lentils are tender. This will take about an hour if you're using urad dal, less for other varieties. Drain any excess water when the lentils are done cooking.

When the lentils have about 30 minutes cook time left, coat the bottom of a medium pot with 2 tablespoons of vegan butter. Place over medium heat and melt the butter. Add the tofu and cook for about 10 minutes, flipping once or twice, until the cubes are browned on multiple sides. Remove the tofu from the pot and transfer it to a plate.

Add the remaining vegan butter to the pot and allow it to melt. Add the onion and sauté until soft and translucent, about 5 minutes. Add the serrano pepper, garlic, ginger, garam masala, cumin, turmeric, and cardamom. Sauté for about 1 minute more, until very fragrant. Return the tofu to the pot and stir in the crushed tomatoes, broth, and sugar. Raise heat and bring the mixture to a simmer. Allow to cook until the sauce thickens up a bit, about 20 minutes. Stir in the lentils and yogurt. Allow to cook another minute or two, just until heated throughout. Remove from heat and season with salt and pepper to taste. Adjust any other seasonings to your liking.

Divide the tofu and lentils onto plates and top with a sprinkle of cilantro. Serve with basmati rice.