This recipe is a template–most greens will work here.

1 large onion, thinly sliced
6 to 8 cloves garlic, or to taste, thinly sliced
1 bunch rapini, or other greens
olive oil
1/4 – 1/2 t red pepper flakes, or to taste
salt, to taste
1/2  – 3/4 pound penne pasta (2  – 3 c dried)
red wine vinegar
grated Romano  or Parmesan cheese

1. Wash the rapini, separate the heavy stems from the leaves, and chop the stems, if you want to use them, and the leaves. Put a large pot of water on to boil.

2. Liberally cover the bottom of a saute pan with the olive oil and saute the onion (and chopped stems, if using) over medium heat . When the onion has begun to wilt and brown a little, add the garlic, the pepper flakes, and salt. Toss briefly, then add the rapini with a splash of water. Lower the heat and cook until tender, stirring or tossing frequently.

3. Meanwhile, cook the pasta. Taste the rapini mixture for seasoning, then add a generous amount of olive oil and a splash of red wine vinegar. Toss with the cooked, drained pasta, and sprinkle with grated cheese. Have more grated cheese at the table.