3 tablespoons olive oil
1 small lemon, very thinly sliced, seeds removed
2 sundried tomatoes, packed in oil
2 leeks, white and pale green parts only; washed, trimmed and thinly sliced
4 garlic cloves, thinly sliced
½ bunch broccoli rabe, chopped
Kosher salt and freshly ground black pepper
2 15-oz. cans white beans, rinsed
¼ cup fresh flat-leaf parsley leaves
2 tablespoons finely grated Parmesan, plus more for serving
Crushed red pepper flakes (optional)