Add the pasta and cook according to the package directions.Meanwhile, in a medium bowl, combine the pear and lemon juice, and toss to coat the pear evenly to prevent them from turning brown.In a sauté pan over medium-high heat, melt 2 tablespoons of the butter.
Add the pears and sugar and caramelize. Set pears aside on a plate.
Add the remaining butter and onions and saute until tender.
Add the cream and reduce the heat to low and simmer for about 1 minute.
Add 1/2 a cup of the cheese and whisk until smooth, about 1 minute more.
Remove from the heat and season with salt and pepper.dd the pears, walnuts, arugula and basil and stir.
Drain the pasta in a colander, add to the sauce and toss well.