Caramelize the onions: In your largest Dutch oven or heavy pot, heat 2 tablespoons of the olive oil over medium-high heat. Add the onions, 1/2 teaspoon salt, and 1/16 teaspoon pepper and cook, stirring occasionally and letting the onions stick to the pan a little to brown but not burn, about 25 minutes. Reduce the heat to medium if the onions are browning too fast or burning. Add 2 tablespoons water and continue to cook, stirring, for another 6 to 8 minutes or until onions are soft and golden brown. Set aside to cool.
Warm a saucepan over medium heat with remaining 1 tablespoon olive oil. Add the pancetta and cook, stirring until lightly browned, 10 to 12 minutes. Remove and reserve the pancetta, remove all but 1 tablespoon of grease from the pan, then rewarm the pan over medium heat, add the kale, and toss until slightly tender, 1 to 2 minutes. Set aside.
In a blender, blend the eggs on medium-high speed until foamy, about 30 seconds. Add the half-and-half, sour cream, sea salt, 1/8 teaspoon pepper, and pinch of cayenne. Blend until smooth, up to 15 seconds.