2 tablespoons olive oil
1/2 medium white onion, finely chopped
4 medium garlic cloves, finely chopped
Freshly ground black pepper
2 pounds beet greens, washed, ribs removed, and coarsely chopped (about 11 cups)
1 pound penne pasta
5 ounces crumbled feta (about 3/4 cup)
Bring a large pot of heavily salted water to a boil. Meanwhile, heat the olive oil in a large frying pan over medium heat. When shimmering, add the onion and garlic, season with salt and pepper, and cook until the vegetables are translucent, about 3 minutes.
Add the beet greens and cook until just wilted, about 3 minutes. Season well with salt and pepper, remove from heat, and reserve. Meanwhile, cook the pasta according to the package directions. Drain the pasta, reserving 1 cup of the cooking water.
Return the pasta to the pot and place over low heat. Add the reserved pasta water and the beet green mixture, then sprinkle in the crumbled feta. Stir until thoroughly combined and heated through. Taste and adjust the seasoning as needed.