Bring a large pot of water to a boil, then salt it heavily. You want about 2 tablespoons of kosher salt per pound of pasta. Cook the pasta until al dente, about 2 minutes under the package instructions. Make sure to reserve about 1 cup of starchy pasta water. Do not rinse the pasta, simply set it aside. If desired, you can add a little bit of olive oil to the cooked pasta and give it a quick toss to prevent it from sticking together.
Season the shrimp with 1 teaspoon of salt, ¼ teaspoon of red pepper flakes, and 2 teaspoons of cajun seasoning, reserving some for later. Add most of the olive oil to the skillet, and increase the heat to medium-high heat. Cook the shrimp for about 60-90 seconds per side until cooked through. If necessary, sear the shrimp in batches to avoid overcrowding the pan. Once cooked, remove from the skillet and set aside.
To the same skillet, add a splash of chicken stock to deglaze the pan, scraping the browned bits off the bottom of the pan with a wooden spoon. Add a little more olive oil, followed by the sausage rounds in a single layer. Sear for about 60-90 seconds per side until browned and crispy. Remove from the skillet.
To the same skillet, add the butter and melt, followed by the fresh thyme and garlic, stirring constantly until the garlic is fragrant. Immediately add the onion and bell peppers with a pinch of salt to cool down the garlic.
Sauté the bell peppers and onions for 3-4 minutes until softened, then, add in the tomato paste. Cook until the color of the tomato paste has deepened, about 2-3 minutes, then deglaze the pan with the rest of the chicken stock.
Reduce the heat to low, then pour in the heavy cream and stir. Add the remaining seasonings to taste, and allow the sauce to gently simmer for 2-3 minutes until it thickens slightly.
Add the cooked pasta and freshly grated parmesan cheese. Slowly stream in the pasta water and toss to help the sauce stick to the noodles, and until the texture of the sauce is to your liking. Add the cooked shrimp and sausage back to the skillet, then toss again to combine.
Garnish with fresh parsley, and more parmesan cheese if desired. Enjoy!
Store leftovers in an airtight container in the fridge for up to 3 days. Reheat gently on the stovetop, by adding a splash of pasta water over medium-low heat until warmed through. If possible, store the noodles separately from the proteins and the sauce, as the noodles will continue to absorb the sauce, making them mushy. Do not freeze.