Place the cremini mushrooms and walnuts in a food processor and pulse until they reach a fine, crumbly consistency similar to ground meat.
Crumble the tempeh by hand into small bits.
In a non-stick skillet over medium heat, add the vegetable broth and the mushroom-walnut mixture.
Sauté for 5 minutes until the mushrooms have released their moisture and the broth has mostly evaporated.
Add the crumbled tempeh, cooked lentils, chili powder, cumin, garlic powder, and onion powder to the skillet.
Cook for another 5-7 minutes, stirring frequently, until the mixture is well-combined and slightly browned.
Remove from heat and stir in the nutritional yeast to add a savory, umami depth.
Warm the corn tortilla in a separate dry pan or over an open flame for 30 seconds per side.
Fill the tortilla with the plant-based meat mixture.
Top with fresh salsa and cilantro, then serve with a lime wedge for squeezing over the top.