1 pound broccoli (stalks peeled and ends trimmed, cut lengthwise into long spears)
  Kosher salt
2 tablespoons olive oil
1 small yellow or white onion (halved through the root end and then sliced thin)
  pinch red pepper flakes (or to taste)
2 anchovy fillets (mashed to a paste with a fork)
2 large cloves of garlic (thinly sliced)
2 teaspoons fresh thyme leaves (minced)
1/2 lemon (optional)