Cut off the woody ends of the broccoli then blanch them in lightly salted boiling water for about 4 minutes. Drain and keep warm.
Roughly chop the nuts, then dry-fry them in a frying pan. Transfer them to a plate.
Cut the onion in half, then slice into thin strips. Roughly chop the garlic. Heat the oil in a frying pan and gently cook the onion and garlic until they soften. Add the chopped anchovies and the drained beans. Cook for another 5 minutes, until the anchovies become mushy. Season with salt and pepper.
Arrange the broccoli on a serving plate and spoon the onion mixture on top, then scatter with the nuts. Finally, squeeze the lemon juice over the dish.