Bring a large pot of water to a boil and add chicken bouillon paste. Boil pasta until al dente, according to package instructions. Reserve 1 cup of the pasta water, and drain. We’ll use that pasta water later!
Season the shrimp. Season shrimp with 1 tsp cajun seasoning, kosher salt, and black pepper. Set aside.
Add olive oil to a large skillet over medium heat. Add andouille sausage and cook until browned on both sides, 5-7 minutes. Remove from the pan and set aside.
Cook the shrimp. Add shrimp to the pan and cook for 2-3 minutes, until slightly curled and pink (no longer translucent). We intentionally cooked the sausage first so the shrimp cooks in its fat. Remove and add to the bowl with the sausage.
Sauté the aromatics. Using the leftover juices in the pan, add onion, bell peppers, and celery to the skillet and cook for 5-7 minutes until the vegetables begin to soften and brown. Add a little more olive oil if needed. Then add garlic and continue to cook for an additional 2 minutes.
Add tomato paste, garlic powder, onion powder, and remaining cajun seasoning. Mix together until the paste is warmed and mixed in with the veggies, about 3-4 minutes. Then add chicken broth to and diced tomatoes. Use the juices to deglaze the pan - be sure to get those browned bits on the bottom of the pan. It's where all of the flavor is!
Then add heavy cream. Reduce heat to low and cook until a thick sauce forms, stirring occasionally, about 5-7 minutes.
Add in spinach, parmesan, and lemon juice and stir until combined and the spinach is cooked down into the sauce. Add 1/2 cup of the pasta water to thin the sauce (add the entire cup if you prefer a very thin sauce). Stir until the sauce is creamy.
Taste for salt and pepper and adjust as needed.
Add in the cooked pasta and top with shrimp, sausage, and fresh parsley.
Notes
Pro Tips for Making Creamy Cajun Shrimp Pasta
If you're meal prepping this Cajun pasta, cook the sauce separately and just boil the pasta when you're ready to serve. This will prevent the pasta from getting mushy in storage.
Don't forget to reserve pasta water! We need it to slightly thin the sauce and help it cling to the pasta. Reserve at least a cup before draining your noodles.
Take your time sautéing the aromatics and tomato paste. This intensifies the flavors of the sauce – otherwise, it'll taste flat. Let those onions, peppers, and celery soften and caramelize a bit, then let the tomato paste cook until it deepens in color and becomes fragrant.
Don't overcook the shrimp! As soon as the shrimp is pink and slightly curled (In the shape of a "C"), remove from the heat.
All cajun seasoning blends are not the same! Some blends are saltier than others so be sure to taste the sauce as you cook.
Substitutions and Variations
Pasta - Aside from casarecce or penne, you can also use rigatoni, fettuccine pasta, linguine, spaghetti, fusilli, and other sturdy noodles for this creamy cajun shrimp pasta with sausage.
Protein - Add chicken or other types of seafood like catfish, scallops, or salmon like this Cajun Salmon Pasta. You can even make this with tofu.
Keto and gluten-free - Make it keto by replacing the penne with spaghetti squash or zucchini noodles. For a gluten-free version, just use gluten-free pasta (the rest of the recipe is already gluten-free)!
Turn this cajun shrimp and sausage pasta alfredo into a cheesy pasta bake! Top with mozzarella or mild cheddar and bake at 350F for 10-15 minutes until golden and bubbly.
Add chopped jalapenos, red pepper flakes, or more cayenne powder for a spicier pasta dish.
For a lighter version, skip the heavy cream and parm.