Kale, Sweet Potato & Onion Frittata

Method

1. Preheat the oven to 450°F.
2. In a large bowl, beat the egg whites with an electric hand mixer until soft peaks form.
3. Add the egg yolk and gently fold with a rubber spatula until incorporated. Refrigerate while you cook the vegetables.
4. In a large, nonstick, oven-safe skillet, combine the sweet potato and water. Bring to a boil over high heat, then reduce the heat to low and simmer, stirring occasionally, until the water has evaporated and the sweet potato is soft on the outside, about 8 minutes.
5. Add the onion, olive oil, salt, and pepper. Increase the heat to medium and cook, stirring often, until the onion starts to soften, about 1 minute.
6. Add the chopped kale and cook, stirring often, until the kale is wilted and dark green, about 2 minutes more.
7. Spread the vegetables evenly over the bottom of the skillet, then pour the egg mixture on top and spread in an even layer.
8. Transfer the pan to the oven and bake until the frittata is puffed, cooked through, and very lightly browned on top, 5–6 minutes.
9. Let the frittata cool in the skillet for 5 minutes, then flip it onto a cutting board and cut in half.
10. Cut the frittata into wedges, then serve with orange slices. Let any leftovers cool completely, then store in an airtight container in the refrigerator.