Meanwhile, in a large lidded skillet over medium-high heat, add 2 tbsp. EVOO, two turns of the pan, then stir in the onions and garlic. Season with salt and pepper. Cook until just softened, 4 to 6 minutes. Stir in the wine and bring to a simmer. Stir in the kale and a pinch of salt and pepper; cover pan with a lid. Cook until kale is wilted, 3 to 5 minutes. Uncover and add the lemon zest and nutmeg, stirring until the liquid evaporates, about 30 seconds. Stir in the cooked pasta, 1/2 cup of reserved pasta water, and the juice of half the lemon. Stir until well combined. Add the pecorino and half the walnuts. Cook, stirring constantly, until pasta is saucy, adding more pasta water if needed. Season with salt, pepper, and more lemon juice, if desired.