Preheat your oven to 400°F and line a large baking sheet with parchment paper for easy cleanup.
Peel and dice the sweet potato into 1/2-inch cubes and cut the chicken breast into uniform bite-sized pieces.
Place the sweet potato cubes and chicken on the prepared baking sheet, then toss with olive oil, sea salt, black pepper, and garlic powder until evenly coated.
Roast in the oven for 20-25 minutes, tossing halfway through, until the sweet potatoes are golden-brown and the chicken is fully cooked.
While the base roasts, remove the tough ribs from the kale and finely chop the leaves.
Place the kale in a large bowl and massage it with half of the lemon juice for 1-2 minutes until the leaves are softened and dark green.
In a small ramekin, whisk together the tahini and the remaining lemon juice, adding a teaspoon of warm water if needed to reach a creamy, pourable consistency.
Divide the massaged kale into bowls, top with the roasted chicken and sweet potatoes, and finish with a drizzle of the tahini dressing.