http://www.bonappetit.com/recipe/white-beans-broccoli-rabe-lemon
Heat oil in a large Dutch oven or heavy pot over medium heat. Add lemon, anchovies, and garlic. Cook, stirring occasionally, until lemon is softened and brown in spots and anchovies fall apart, about 5 minutes. Add broccoli rabe; season with salt and pepper and cook, tossing occasionally, until bright green and crisp-tender, about 5 minutes.
Add beans and ½ cup water to pot. Bring to a boil; reduce heat and simmer, stirring occasionally, until flavors have melded and liquid is reduced by half (you still want it to be saucy), about 5 minutes. Mix in parsley and 2 Tbsp. Parmesan.
Transfer to a platter, sprinkle with red pepper flakes, if desired, and top with more Parmesan.