In a bowl, toss the shrimp with lemon juice, olive oil, Cajun seasoning, garlic powder, smoked paprika, and dried oregano. Let them marinate while you prepare the other ingredients.

Heat a drizzle of oil in a large skillet over medium-high heat. Add the shrimp and cook for 1-2 minutes per side until they turn pink and opaque. Remove from the skillet and set aside.

In the same skillet, melt 2 tablespoon butter and sauté the diced onion for 5 minutes until soft and fragrant. Add 1 teaspoon salt to help them break down.

Pour in the heavy cream and remove the pan from heat for a moment. Stir in the flour slurry to prevent lumps.

Return to low heat and add the Cajun seasoning, garlic powder, smoked paprika, and dried oregano. Stir until combined.

Return the cooked shrimp to the skillet and stir in chopped parsley and the Boursin cheese. Let it melt into the sauce, stirring occasionally. Simmer for 5 minutes to blend all the flavors.

Meanwhile, cook the penne in a large pot of salted boiling water until al dente. Before draining, reserve ½ cup of pasta water. Rinse the pasta with cold water to maintain its texture.

Add the cooked pasta to the skillet along with a splash of reserved pasta water. Toss everything together and let it simmer for 5 minutes, allowing the sauce to thicken and coat the pasta beautifully.

Taste and adjust seasoning if needed. Serve hot, garnished with grated Parmesan, extra parsley, and a sprinkle of black pepper.