Preheat oven to 350ºF (225°C). Heat the olive oil in a 10-inch nonstick skillet over medium heat. Add the sausage and cook until browned, breaking it up into small chunks as it cooks, 3 to 4 minutes. Add the green and red peppers and the onion and garlic powder. Cook, stirring often, until the vegetables are soft, 4 to 5 minutes. Add the kale and cook, stirring occasionally, until it wilts and softens, about 3 minutes. Remove from the heat.
Meanwhile, in a bowl, whisk together the eggs, heavy cream, salt, and pepper. Stir in the cheese.
Add the egg mixture to the pan of vegetables, then briefly stir with a wooden spoon to gently mix everything together and evenly distribute it in the pan. Let the frittata set over the heat without touching it for 3 to 4 minutes, then transfer it to the oven and bake until it puffs up and is set when you jiggle it, about 15 minutes. For easiest removal from the skillet, let the frittata sit for a few minutes so the edges pull away from the sides of the pan. Serve.