Begin by horizontally slicing the thin boneless skinless chicken breasts to ensure they cook quickly and evenly. Pat them dry with a paper towel, then dredge each piece in a seasoned flour mixture of salt, black pepper, garlic powder, and Italian seasoning.

Heat a large skillet over medium-high heat and add olive oil. Once the oil shimmers, carefully place the dredged chicken in the skillet, cooking for 4-5 minutes on each side until they achieve a beautiful golden brown color and are cooked through. Remove the chicken from the skillet and set aside.

In the same skillet, reduce heat to medium and add butter, allowing it to melt. Toss in chopped yellow onion and sauté until translucent, around 3-4 minutes. Add minced garlic and diced tomatoes. Sprinkle a little flour into the mixture and pour in white wine. Let it simmer for a minute before adding heavy cream, Italian seasoning, and crushed red pepper flakes.

While the sauce simmers, bring a pot of salted water to a boil and cook the spaghetti according to package instructions until al dente, about 8-10 minutes. Reserve a cup of pasta water and drain.

Once the sauce is creamy, add cooked spaghetti to the skillet and toss it with the sauce on low heat for about 2-4 minutes. If the sauce is too thick, add a splash of the reserved pasta water until desired consistency is reached. Return the chicken to the skillet and heat through for another minute.

Serve the creamy chicken pasta on plates, placing the tender chicken atop or beside the spaghetti. Garnish with freshly grated Parmesan cheese and additional crushed red pepper flakes if desired.