Preheat the oven to 375ºF and prepare a baking sheet with foil.

In a large bowl, toss the potato with 3/4 of the oil, chili, cayenne, cumin, and 2/3 of the salt.

Roast the potatoes in the oven for 12-15 minutes, until tender.

While the potato is baking, in the same bowl you used for the potatoes, combine the beans, remaining salt, remaining oil, and the portion of cilantro for the beans in the ingredient list. There will be some leftover spices on the sides of the bowl from coating the potato, that you can incorporate into the beans as you stir.

When the potato is cooked, add, to the beans, and gently toss to combine.

In a food processor, pulse together the portion of cilantro called for in the sauce and garlic until finely chopped. Add the yogurt, sour cream, salt, pepper, and lime, then process until smooth. Add the oil while the processor is running.

Place the tortillas between two damp towels and microwave for 20 to 30 seconds. Top the tortillas with the cilantro lime cream sauce, bean-potato mixture, and a dollop of sour cream.