In a cast iron skillet, heat the oil over medium-high heat.
Add in the lean ground turkey, garlic, onion, and pepper. Cook until the turkey is browned. This will take about 10 minutes or so.
Add in the diced sweet potatoes, salt, pepper, and red pepper flakes.
Cover the skillet and continue to cook until the sweet potato is soft. This will take about 15-20 minutes. Stir occasionally.
Preheat the oven to 400°.
When the sweet potatoes are soft, sprinkle on the cheese and pop the uncovered skillet into the oven for 2-5 minutes. You just want to the cheese to melt, so keep an eye on it. Like...don't walk away.
Take it out of the oven and enjoy! I think the beef tallow gives it a great flavor but any of the oils will work.