Bring a large pot of water to a boil and cook the pasta to al dente, strain then set aside, leaving ¼ cup of pasta water for the sauce.
In a large frying pan on medium heat, cook the sausage until browned, approximately 5 minutes. Spoon out the sausage into a separate bowl.
To the same pan, add in the garlic and shallot then cook until fragrant. Add in the tomato paste, bell peppers and cajun seasoning, stirring to combine.
Pour in the half and half and stir and pasta water, bringing the cream to a rolling boil.
Pour in the pasta and add in the grated Manchego cheese, stirring to combine.
Add the sausage back in and stir to incorporate.
Top with additional Manchego and garnish with optional red pepper flakes and serve.