In a large skillet, melt butter over medium heat. Sauté onion until tender, about 5 minutes. Stir in the garlic and cook until fragrant, about 1 minute.
Remove from heat. Pour cooked onions and garlic into a high powered blender. Add in red peppers, chicken stock, salt, pepper and basil. Blitz until smooth. Feel free to add in a little cream to get things moving.
Pour back into hot pan and stir in cream. Cook over low to medium low heat until your cooked pasta is al dente. {You don't want it to boil! The cream will curdle...ew!}
Once pasta is cooked, pour into the sauce along with parmesan cheese and toss. Taste, adjust salt and pepper and serve!