Add 2 teaspoons of oil to a medium skillet (I used a cast iron skillet), add fajita veggies and 1 teaspoon of taco seasoning. Sauté veggies until tender and hot, about 5-7 minutes. Move to a bowl.
Crumble tempeh into small pieces using your hands and add to a bowl with tamari, lime juice and 1 Tablespoon taco seasoning.
In the same skillet you used to cook the veggies, add another 2 teaspoons of oil and add tempeh mixture into the skillet. Cook, stirring frequently until tempeh starts to brown and is warm throughout, about 5-7 minutes. Remove from skillet and start building tacos.
For tacos fill one tortilla with tempeh, fajita veggies, slaw and avocado slices. Top with tomatillo dressing. Add salsa, hot sauce, pickled onions and a squeeze of fresh lime juice, if using.