Preheat oven to 375°F. Spray a large glass baking dish with cooking spray.
Heat a large skillet over medium heat and add ½ tbsp olive oil. Add the diced sweet potatoes and onion and saute. Once simmering, add a lid and cook for about 10 minutes (or until sweet potatoes are tender enough to pierce with a fork), stirring every couple of minutes. Once cooked, remove potato and onion from pan and set aside.
Add the turkey sausage to the pan and saute until browned. Remove from pan and set aside.
Add kale to the pan, add the lid, and cook for 3 minutes (or until just wilted), stirring halfway through to prevent burning.
Add cooked vegetables and turkey sausage to the prepared baking dish. In a large bowl, beat eggs, salt, pepper, and crushed red pepper flakes. Pour egg mixture into the baking dish. Give the dish a gentle shimmy to ensure everything is evenly distributed.
Bake for 32 minutes or until eggs are set. Serve immediately or store for up to 4 days.