Heat butter and oil to a large sauté pan over medium heat. Once the butter has melted, add the sliced onions and cook for about 10 minutes, stirring every few minutes, until soft and golden. Season with a pinch of salt, then reduce the heat to medium-low (or low) and continue cooking for about 20-30 minutes, until onions are caramelized to your desired color.

Add 1-2 tablespoons of water to the onions right before they’re done cooking to deglaze the pan. Turn off the heat, remove the onions, and set aside.

While the onions are caramelizing, cook the pasta according to package directions until al dente. Reserve 1 cup of pasta water, then drain and rinse the pasta.

Add the sausage to the same pan and cook over medium heat. Break it into small pieces with a spatula and cook until browned and cooked through. Add the minced garlic, chopped sun-dried tomatoes, Calabrian chili, and Italian seasoning. Cook for about 1 minute, until fragrant.

Reduce the heat to low, then return the caramelized onions to the pan and mix well. Pour in the heavy cream and reserved pasta water. Stir to combine and bring to a gentle simmering. Add the pasta, grated Parmesan, and chopped parsley, then toss until everything is well combined and coated in sauce.

Season with salt and pepper to taste. Serve warm & enjoy!