Preheat your oven to 375 degrees F. Grease a 9x13 inch baking dish lightly with cooking spray or a thin coat of olive oil. Set it aside.

Heat the olive oil in a large skillet over medium-high heat. Add the diced onion and cook for 3 to 4 minutes until it softens. Add the garlic, cumin, chili powder, and smoked paprika and stir for 30 seconds until you can smell the spices blooming. Add the ground turkey and break it apart with a spoon. Cook for 7 to 8 minutes, stirring regularly, until the turkey is completely browned and no pink remains. Drain any excess liquid from the skillet.

Stir in the drained diced tomatoes, tomato paste, and chicken broth. Season with 1/2 teaspoon salt and 1/4 teaspoon pepper. Let the mixture simmer for 3 minutes so it tightens up slightly. It should look saucy but not watery. Remove from heat.

Arrange half of the sweet potato slices in an even layer on the bottom of the prepared baking dish. Season them lightly with a pinch of the remaining salt and pepper. Spoon the turkey mixture evenly over the sweet potato layer. Arrange the remaining sweet potato slices on top of the turkey in an overlapping layer, like shingles. Season the top layer of sweet potatoes lightly with the last of the salt and pepper.

Cover the dish tightly with aluminum foil. Bake at 375 degrees F for 25 minutes covered. This steams the sweet potatoes so they become tender all the way through without drying out.

Remove the foil and scatter the shredded cheddar evenly over the top. Return the dish to the oven uncovered for 20 to 25 minutes until the cheese is fully melted and bubbling at the edges and the sweet potato slices on top are tender when you press them with a fork.

Let the casserole sit for 5 minutes before cutting and serving. Scatter fresh cilantro or parsley over the top. Serve directly from the baking dish.