Cook pasta in salted water according to package directions. Melt 2 tablespoons butter in a large skillet over medium-high heat. Add the onions and garlic and saute for 2 to 3 minutes or until starting to soften. Add the chopped red peppers and cook for 2 to 3 minutes, until hot. Remove the skillet from the heat. Carefully transfer the contents of the skillet to a food processor or blender. Place on the lid and puree the pepper mixture until totally blended (there will still be some texture to the peppers.) Heat the other 2 tablespoon butter back to the skillet over medium heat. Pour the pepper puree back into the skillet. Add the broth, salt, and pepper, and stir until heated. Splash in the cream and stir to combine. Taste and adjust seasonings if you need to.Drain the pasta and add it to the skillet. Add Parmesan and parsley/basil, then stir it together to coat the pasta. Serve in bowls with extra Parmesan and a sprinkling of parsley on top.