I really love kale in a primal version of Spanish Tortillas. Just leave out the potato, add more onion, and use less olive oil and don't drain it. I practically lived on tortillas in Spain, they're so freakin' delicious.
It's a laborious recipe but I enjoy making it for a culinary treat on the weekends. I tried it once with chopped bacon but it made the bacon soggy, and honestly the flavor of the tortilla doesn't need the help. The texture of kale holds up in the tortilla better than spinach, which is too tender and tends to flatten in clumps while cooking. It's yummy hot or cold (how you'd frequently get it in Spain). I'm sure kale be great in a crustless quiche/breakfast casserole/other egg configuration as well. Hope this helps!