To make the lentil walnut "meat," place the walnuts and seasonings in a food processor fitted with the S blade. Process for about 1 minute, until everything is ground into a meal. Add the tomato paste and the cooked lentils. Pulse until you have a crumbly, uniform mix (see photo above—about 15 seconds of pulsing).
Heat the oil, water or broth in a large skillet (one that has a lid) over medium heat. Add the onion and zucchini. Cook, stirring occasionally, for about 5 minutes, until the onion is soft and clear. Add the lentil walnut meat and reduce the heat to low. Cook, stirring frequently, for 2 minutes, or until the lentil and walnut mixture has heated through. Finally, stir in the rice and tomatoes.
Warm all ingredients through, stirring gently. Add the lime juice. Taste the mixture and add as much salt and freshly ground pepper as you like. Serve hot, with nutritional yeast or a sauce if desired.