Pesto Pasta - Diamond Nuts

Ingredients

• Walnut Pesto
• 1/2 cup Diamond walnuts
• 1 garlic clove, minced
• 1 1/2 cups packed arugula leaves
• 1/2 cup fresh basil leaves
• zest and juice from 1 lemon
• 1/2 cup grated parmesan cheese
• 1 teaspoon kosher salt
• 1/2 teaspoon freshly ground pepper
• 1 cup extra virgin olive oil
• Pasta
• 1 lb. long fusilli
• 2 tablespoons unsalted butter, divided
• 2 tablespoons olive oil
• 1 large yellow onion, sliced (about 2 cups)
• 2 - ­8 ounces packaged sliced crimini (baby bella) mushrooms
• 1/2 cup parmesan, grated (plus more for garnish)
• juice from 2 lemons (about 1 ⁄ 3 cup)
• 3/4 cup roasted red peppers, diced
• kosher salt and freshly ground pepper