Cook the broccoli rabe in a large pot of boiling salted water until crisp tender, about 1 minute. Transfer the broccoli rabe to a large bowl of ice water to cool, saving the cooking water. Bring the reserved cooking water back to a boil.
Heat the oil in a heavy large skillet over medium heat. Add the sausage and cook, breaking it up into pieces with a spoon, until browned and juices form, about 12 minutes. Add the garlic and red pepper flakes, and saute until fragrant, about 2 minutes.
Meanwhile, when the reserved cooking water is boiling, add the orecchiette and cook until al dente, tender but still firm to the bite, stirring occasionally, about 8 minutes.
Strain the broccoli rabe and add it to the pan with the sausage mixture and toss to coat with the juices. Add the pasta to the skillet. Stir in the Parmesan and serve immediately.
Simple Tomato Sauce:
In a large casserole pot, heat oil over medium-high heat. Add onion and garlic and saute until soft and translucent, about 2 minutes. Add celery and carrot and season with salt and pepper. Saute until all the vegetables are soft, about 5 minutes. Add tomatoes, basil, and bay leaves and reduce the heat to low. Cover the pot and simmer for 1 hour or until thick. Remove bay leaves and taste for seasoning. If sauce tastes too acidic, add unsalted butter, 1 tablespoon at a time, to round out the flavor.
Pour half the tomato sauce into the bowl of a food processor. Process until smooth. Continue with remaining tomato sauce.
If not using all the sauce, allow it to cool completely and then pour 1 to 2 cup portions into plastic freezer bags. Freeze for up to 6 months.