01 - Bring a large pot of generously salted water to a rolling boil. Add the fettuccine and cook according to package directions until perfectly al dente. Drain, reserving approximately 1/2 cup of the starchy pasta water, and set the pasta aside.
02 - While the pasta is cooking, heat 1 tablespoon of olive oil in a large skillet over medium heat. Add the thinly sliced purple cabbage and red onion. Sauté for 3-4 minutes, or until they begin to soften. Remove from skillet and set aside.
03 - Using the same skillet, add another tablespoon of olive oil. Introduce the thinly sliced yellow bell pepper and corn kernels. Cook for 3-4 minutes, until the pepper is tender-crisp and slightly golden. Remove from skillet and set aside.
04 - Add the final tablespoon of olive oil to the skillet. Add the broccoli florets and sauté for 2 minutes. Then, stir in the fresh spinach and cook until just wilted, approximately 1 minute. Remove from skillet and set aside.
05 - In the same skillet, add the minced garlic and sauté for about 30 seconds until fragrant. Pour in the heavy cream and bring to a gentle simmer. Stir in the grated Parmesan cheese and the Cajun seasoning, if using. Season with salt and black pepper to your preference. Allow the sauce to simmer for 3-4 minutes, stirring occasionally, until it achieves a slightly thickened consistency.
06 - Add the drained fettuccine to the skillet with the prepared sauce. Toss gently to ensure every strand is evenly coated. If the sauce seems too thick, gradually incorporate a splash of the reserved pasta water to achieve a silkier texture.
07 - Divide the sauced pasta among individual serving plates. Artfully arrange the sautéed purple, gold, and green vegetables in distinct sections on top of the pasta to create vibrant color layers. Garnish generously with chopped fresh parsley and serve with optional lemon wedges on the side for a bright finish.