For an extra layer of flavor, consider marinating the tempeh in the fajita seasoning mixture for at least 30 minutes before cooking. Serve these Vegan Fajitas with Tempeh in warm tortillas, with your favorite toppings such as salsa, guacamole, vegan sour cream, or cilantro. To add some heat, include a pinch of cayenne pepper or a finely chopped jalapeño to the skillet along with the other vegetables. Experiment with different colored bell peppers for a more visually appealing dish.