Cook aromatics: Heat the oil in a large skillet over medium-high heat. Cook the onion and garlic for about 3 minutes, or until fragrant.
Add the lentils, and walnuts and cook for 1 minute more. (See notes.)
Add the spices, and tomato paste and cook for 2 minutes, stirring constantly.
Pour in the tamari, and vegetable broth. Reduce the heat to low and cook for about 4 minutes, or until the mixture thickens, adding more broth as desired.
Season: Add fresh lime juice to taste. Season with salt and pepper. Garnish with chopped cilantro, if using.