Preheat oven to 425. Toss diced sweet potatoes in olive oil, corn starch, and salt. Spread sweet potatoes out on a rimmed backing dish in a single layer (the more space they have, the crispier they'll get). Bake in oven, flipping potatoes every 15 minutes until cooked through and crispy on the edges.
While sweet potatoes cook, prep kale and red onion. In a small bowl or jar with lid, pour 1/4 cup (or less or more to taste), lemon juice, and salt and pepper. Whisk or shake together.
In a large bowl, add kale, sweet potatoes, onions, pumpkin seeds, and parmesan. Toss together with your olive oil dressing and enjoy!