Pat the chicken cutlets dry with paper towels: Season both sides with 1 1/2 tablespoons of the Cajun seasoning, 3/4 teaspoon of the salt, and all of the black pepper.

Bring a 5- to 6-quart pot of water to a rolling boil. Add 1 tablespoon fine salt and the fettuccine. Cook according to the package directions until al dente, usually 10 to 12 minutes.

Before draining, scoop out 1 cup (240 ml) of the starchy pasta water. Drain the fettuccine without rinsing and set it aside.

While the pasta cooks, heat the olive oil and 1 tablespoon (14 g) butter in a 12-inch skillet over medium-high heat.

Add half of the chicken cutlets in a single layer. Cook for 3 to 4 minutes, until the underside is deeply golden and releases easily from the pan.

Turn and cook for another 2 to 4 minutes, until the thickest part reaches 165°F (74°C). Transfer to a clean plate. Repeat with the remaining chicken, adding the remaining 1 tablespoon (14 g) butter if needed.

Let the chicken rest for 5 minutes while you prepare the Alfredo sauce.

Reduce the skillet heat to medium-low: Add the garlic and cook for about 30 seconds, stirring constantly, until fragrant but not browned.

Pour in the heavy cream: Stir in the remaining 1/2 tablespoon Cajun seasoning and remaining 1/4 teaspoon salt. Bring to a gentle simmer and cook for 3 to 4 minutes.

Reduce the heat to low: Add the 1 1/2 cups (135 g) Parmesan in three additions, whisking until each portion melts before adding the next. Do not let the sauce boil.

Whisk in 1/2 cup (120 ml) of the reserved pasta water. The sauce should look smooth and glossy and be thick enough to coat a spoon while still flowing easily.

Transfer the drained pasta to the skillet and toss gently with tongs for 1 to 2 minutes. Add more reserved pasta water, a few tablespoons at a time, if the sauce becomes too thick.

Remove the skillet from the heat and stir in the lemon juice. Taste before adding any additional seasoning because the Cajun blend and Parmesan both contribute salt.

Cut the rested chicken across the grain into strips. The interior should be opaque and juicy with no translucent areas.

Divide the Alfredo fettuccine among six plates: Arrange the Cajun chicken over the pasta and garnish with parsley, extra Parmesan, and crushed red pepper flakes as desired.