Bring a large pot of water to a boil over high heat. Season generously with kosher salt. Add the pasta and cook for 2 minutes less than package directions, about 13 minutes. Reserve 1 cup pasta water and drain well.

Meanwhile heat a large skillet over medium high heat. Add the oil and heat another 30 seconds. Add the sausage the sausage to the pan. Cook stirring occasionally and breaking the sausage into small pieces with the back of a wooden spoon, for about 10 minutes or until the sausage is cooked and beginning to brown.

Add the onion and salt and cook another 3 minutes until the onion is soft and fragrant. Add the apples and cook an additional 4 minutes to soften the apples slightly. Add the pasta and half of the crumbled gorgonzola along with the pasta water and stir well to coat. Continue to stir and toss together until the cheese forms a light creamy sauce with the pasta water. Add the arugula and toss well until the arugula is just wilted, another minute. Top with the remaining cheese and serve warm.