Scrub the outside of the sweet potatoes really well. Slice the potatoes into rounds about ¼” thick. Place on baking trays lightly sprayed with cooking spray. Sprinkle the potatoes with salt and chili powder. Place in the oven on 400 degrees F for 15-20 minutes or until tender. Be sure to flip them over halfway through the cooking time so they get a bit brown on both sides.
Remove the potatoes from the oven and set aside to cool. Meanwhile, warm the black beans in a pan on the stove over medium heat.
Combine the diced avocado, tomato, red onion, cilantro and lime juice in a bowl. Stir to combine. Add a bit of salt and pepper to taste.
When the beans are warm, you are ready to assemble. Place the sweet potato rounds closely together, with edges overlapping on a single baking tray or baking stone. Top with black beans, corn, jalapenos and shredded cheese. Place tray in the 400 degree F oven and cook until cheese is melted, about 5 minutes or so.
Before serving, top with tomato mixture and Greek yogurt. Serve with your favorite sauce for dipping.