First, place sunflower seeds in a bowl and cover with hot water; let soak for 30 minutes.
Meanwhile, preheat oven to 400°F. Spread sweet potato on a large rimmed baking sheet and toss with 1 Tbsp. of the oil, and 1/4 tsp. each of the salt and black pepper; bake for 15 minutes.
Remove pan from oven, toss sweet potatoes and push to one side. Add red onion to center of pan, and cubed tempeh to opposite end of pan. (*Note: try to avoid any overlap to encourage browning.) Toss each with 1 Tbsp. of remaining olive oil. Season red onion with remaining 1/4 tsp. salt and black pepper; place back in the oven and bake for 15 minutes.
Remove pan from oven and toss sweet potato and red onion. Brush tempeh with 2 Tbsp. of the BBQ sauce, gently tossing to coat all sides. Place back in the oven for another 15 minutes. Remove pan from oven and brush tempeh with remaining 2 Tbsp. BBQ sauce.
Meanwhile, drain sunflower seeds and transfer to a high speed blender. Add remaining Sunflower Seed Ranch ingredients with the exception of dill and chives. Blend on high speed until creamy; transfer to a bowl and stir in dill and chives.
Lastly, place kale in a large bowl and add one third of the dressing; use your hands to massage dressing into kale until leaves begin to soften and become well-coated. To serve, divide kale evenly into each of 3 bowls, and top with roasted sweet potato, red onion, and BBQ tempeh. Drizzle remaining dressing evenly overtop.