Remove kale ribs, slice kale: Using a sharp paring knife, cut out the rib of each kale leaf. Discard or compost. Slice the leaves roughly 1/2-inch thick.
Cook onion and garlic: Heat olive oil on medium high heat in a large sauté pan. When hot, add the chopped onion. Cook for a couple of minutes until translucent. Add the garlic and cook for a minute more.
Add kale to the onions: Add the kale to the sauté pan. Even if you have a pretty large pan, the kale will be practically falling out of it. Put in as much as you can and use tongs to turn over and mix with the oil and onions. After a couple minutes the kale should wilt a bit so you can add the rest of the raw kale. Cook, turning the kale leaves over occasionally until the kales leaves have wilted and are tender. Sprinkle a little salt over the kale leaves while cooking.
Make tahini sauce: While the kale is cooking, whisk together the tahini, lemon juice, water, 1/2 teaspoon of salt, and dark sesame oil. Add more salt and sesame oil to taste.
Toss cooked kale with sauce: Once the kale is done, toss in the sauce, reserving a little to drizzle on top.Serve, topped with a little sauce and toasted sesame seeds.