In a small bowl, combine ½ cup of the all-purpose flour, salt, black pepper, basil, oregano, and onion powder. Dredge the chicken tenders or halved chicken breasts in the seasoned flour mixture, making sure they're well coated.
In a large skillet, heat 1 tablespoon of olive oil and 1 tablespoon of butter over medium-high heat. Once hot, add the coated chicken and cook for about 5-7 minutes on each side, or until golden brown and cooked through. Remove the chicken from the skillet and set it aside.
In the same skillet, add 2 tablespoons of olive oil. Add the diced red bell pepper and sauté for about 3 minutes, until it begins to soften. Then, add the minced garlic and cook for an additional minute, stirring frequently to prevent burning.
Sprinkle the remaining 1½ tablespoons of flour over the sautéed vegetables and stir well to combine. Gradually pour in the chicken broth while whisking to avoid lumps. Next, add the milk and heavy whipping cream, continuing to whisk until the mixture is smooth and thickened.
Once the sauce has thickened, stir in the chopped spinach and grated Parmesan cheese. Allow the spinach to wilt, which should take about 2-3 minutes. Season the sauce with garlic powder, Italian seasoning, and additional salt and pepper to taste.
While you're preparing the sauce, cook the fettuccine noodles according to package instructions in a large pot of salted boiling water. Once cooked, drain the pasta, reserving a bit of the pasta water in case you want to thin the sauce later.
Slice the cooked chicken into strips and add it to the sauce. Toss in the cooked fettuccine noodles, mixing everything until the pasta is well coated in the creamy Tuscan sauce. If the sauce is too thick, add a splash of the reserved pasta water to reach your desired consistency.
Serve the Tuscan Chicken Pasta warm, garnished with extra Parmesan cheese and fresh herbs, if desired. Enjoy the comforting flavors and creamy texture that make this dish a true crowd-pleaser.