Broccoli Rabe:

1 lb broccoli rabe, ends trimmed

Kosher salt

1 tsp lemon zest

Freshly ground black pepper

Crushed red pepper flakes

Sausage:

1 lb ground meat

1 1/2 tsp coarsely ground fennel seeds

2 garlic cloves, grated

2 tsp brown sugar

2 tsp vinegar

1/2 tsp smoked paprika

1/2 tsp crushed red pepper flakes

1 Tbsp extra-virgin olive oil, plus more for baking dish

Mornay Sauce:

4 Tbsp butter

1/4 cup all-purpose flour

2 1/2 cups whole milk

1/4 tsp freshly grated nutmeg (optional)

1 cup freshly grated Parmesan, plus more for topping

Lasagna:

8 oven-ready lasagna noodles