In a large skillet, heat 3 tablespoons of avocado oil over medium heat. Once hot, add the chopped sweet potatoes, season with salt and black pepper, and sauté for about 10-12 minutes, stirring occasionally, until they are tender and slightly crispy.
Once the sweet potatoes are cooked, add the baby spinach (or your greens of choice) to the skillet. Stir until the greens are wilted, about 2-3 minutes.
In a mixing bowl, beat the eggs with chili powder, salt, and black pepper. Pour the egg mixture into the skillet with the sweet potatoes and spinach. Cook, stirring gently, until the eggs are just set, about 3-5 minutes.
Gently fold in the drained and rinsed black beans, allowing them to warm through for about 2 minutes. Adjust seasoning if necessary.
While the filling is cooking, heat the corn tortillas in a separate skillet over medium heat until warm and pliable. You can also wrap them in foil and warm them in the oven.
To assemble, spoon the sweet potato and black bean mixture onto each tortilla. Top with slices of avocado, cheese (if using), salsa, and a dollop of sour cream or Greek yogurt.
Serve the tacos immediately while they are warm, and enjoy the burst of flavors and textures with each bite!