Preheat the oven to 450°F. Add whole bell peppers and onion to a large baking sheet. Roast for 25-30 minutes until peppers are very soft and charred all over. 

Meanwhile, cook pasta according to pkg directions. Reserved ½ cup pasta water. Drain and set aside. 

Transfer peppers to a cutting board. Use a paper towel to carefully hold the pepper while peeling off the skin using a fork (discard skin). Cut peppers in half. Carve out the inner white lining and seeds. Transfer to a blender along with onion, garlic, cottage cheese, broth, salt, and pepper. Set aside. 

In a medium heavy-bottomed pot, heat oil over medium-high heat. Add sausage and a pinch of kosher salt. Use the back of a spoon to break up sausage into crumbles. Saute for 4-5 minutes until browned and cooked through. Transfer to a bowl. 

In the same pot, pour in roasted pepper sauce. Simer for 5-6 minutes until slightly thickened. Stir in cooked pasta, peas, and sausage. Gradually add pasta water, about 1-2 tbsp at a time, until sauce is smooth and glossy. 

Remove from heat and stir in parmesan and lemon juice. Season to taste with salt and pepper.