Pierce the sweet potatoes a few times with a fork to vent them. Microwave on high for about 5-10 minutes, or until the sweet potatoes are soft throughout. Set aside to cool slightly.

Once cool enough to handle, remove the skin from the sweet potatoes and discard it. Transfer the flesh to a small bowl and mash it with the back of a fork until smooth. Stir in the spices along with some salt and pepper, then mix in the black beans. Set aside.

In another small bowl, combine the avocado, Greek yogurt, and a pinch of salt. Mash together with a fork and set aside.

Heat oil in a large skillet over medium heat. Place a tortilla in the skillet and add the sweet potato mixture to one side. Once the tortilla is warmed through, fold it in half and gently press to seal. Cook until golden brown, about 2-3 minutes per side.

Serve the quesadillas with the mashed avocado.