Wash the greens. Do not dry—the water left on the greens helps them to wilt.
Trim and discard the tougher ribs of the kale. (The chard and mustard green ribs are tender enough that you can chop them along with the leaves.)
Chop the greens in 1 to 1 ½-inch pieces.
Dice the onion into ½-inch pieces.
Bring a large pot of salted water to boil. Cook the pasta until it is tender. (see note)
When the pasta is done, drain and toss with the sun-dried tomatoes and their residual oil. Add a teaspoon of olive oil if needed to keep the pasta from sticking together.
Heat a skillet over medium-high flame. Add the olive oil and the chopped onion.
Cook and stir about 5 minutes, until the onions begin to turn translucent. Stir in the garlic.
Reduce the heat to medium flame. Add the chopped greens and cook, stirring occasionally, until the greens wilt and shrink, another 5 minutes.
Mix the pasta and tomatoes into the greens. Sprinkle in the vinegar and heat through.
Add the walnuts, Aleppo pepper, and salt to taste.