Preheat oven to 350 F.
Remove leaves from stems from 1 bunch kale, and finely chop both.
Cut 1 red onion into long, thin strips.
Heat 1T oil in a large sauté pan over medium heat, add 1 sliced onion and a pinch of salt. Sauté for 5-10 min.
Add chopped kale leaves & stems, cook for 20-25min, add more oil/ lower heat as needed. Turn off heat and allow to cool.
Whisk 12 eggs in a large bowl.
Stir in cooled, sautéed onions & kale, feta crumbles and season with ½ tsp fresh ground black pepper
Pour into an oiled 8x8” or 9x9” pan. Sprinkle w/ 1/8tsp salt.
Bake at for 34-38 minutes or until no longer jiggly.