Preheat oven to 375°F and grease a 9x13-inch baking dish with cooking spray or butter.

Heat 1 tablespoon olive oil in a large skillet over medium heat. Add chopped onion and cook for 3 to 4 minutes, stirring occasionally, until translucent and softened.

Add shredded chicken, cumin, chili powder, salt, and pepper to the skillet. Stir well and cook for 2 to 3 minutes until chicken is heated through and spices are fragrant. Remove from heat.

Warm tortillas by stacking on a microwave-safe plate, covering with a damp paper towel, and microwaving for 30 to 45 seconds until warm and pliable. Alternatively, heat in a dry skillet for about 10 seconds per side.

Lay a tortilla flat and spoon about ¼ cup of chicken mixture down the center. Sprinkle with cheddar and Monterey Jack cheeses, reserving some for topping. Roll tightly around the filling and place seam-side down in the prepared baking dish. Repeat with remaining tortillas, fitting them snugly in the dish.

In a medium saucepan, combine sour cream, heavy cream, and chicken broth. Whisk over medium heat until smooth. Add garlic powder, smoked paprika, cayenne if using, and salt to taste. Cook for 5 to 7 minutes, whisking gently, until sauce thickens slightly. Keep heat at medium-low to prevent separation. Do not let it boil.

Pour creamy sauce evenly over rolled tortillas in the baking dish, making sure each enchilada is coated. Sprinkle remaining shredded cheese over the top, covering completely.

Bake for 20 to 25 minutes until cheese on top is melted, bubbly, and starting to turn golden brown at the edges. Sauce should be bubbling around the edges of the pan.

Let rest for 5 minutes after removing from oven. Top with salsa and fresh cilantro before serving.