In a mortar and pestle, mash the garlic and capers with a pinch of salt to a paste. Blend in the juice from half a Meyer lemon. Then beat in the olive oil. It should semi-emulsify; don't worry if it doesn't.
In a small bowl, combine the onion and thyme leaves with a large pinch of salt, then rub the salt into the onions using your hands. Let sit for 10 minutes.
Put the kale in a large bowl. Add the onion and thyme. Pour in half the dressing and, using your hands, mix the greens—really get in there and work the salad. You should almost knead the greens so they break down a bit and the dressing fully coats the leaves. Taste and add more salt, lemon juice, or dressing, as needed. Let the salad sit for 15 to 20 minutes. Taste and adjust once more. Then spread on a platter and serve.
