In a medium saucepan, heat a drizzle of olive oil over medium heat. Once the oil begins to shimmer, add the tempeh and cook for 6-8 minutes, until golden brown.
Add the soy sauce, garlic powder, chili powder, and cumin, stir, and cook for another 5 minutes, until all of the seasonings are well-distributed and the tempeh is browned. Remove the pan from the heat.
Make the avocado dressing: In a blender, combine the avocado, lime juice, olive oil, salt, and pepper and blend until smooth. Add the water 1 tablespoon at a time until your desired consistency is reached.
Arrange the lettuce, tomatoes, black beans, corn, cilantro, red onion, and tempeh in a large bowl and pour over the avocado dressing.