Bring a large pot of water to a boil over high heat and salt it generously.
Add the angel hair pasta and cook it until just before al dente, then reserve one cup of pasta water and drain the pasta.
While the pasta water heats, warm a large skillet to medium and pour in 2 tablespoons of vegetable oil.
Place the flour mixed with a pinch of salt in a shallow dish, and coat each chicken tenderloin evenly, shaking off any surplus flour.
When the oil is hot, fry the chicken pieces until they turn golden brown on each side, approximately 5 to 7 minutes per side; set aside cooked chicken.
In a medium saucepan over medium heat, melt 2 tablespoons butter, then add diced yellow onion and minced garlic; cook until softened but not browned, about 3 minutes.
Pour in the white wine and let it simmer for two minutes to reduce and evaporate alcohol, scraping the pan bottom for flavor.
Add chicken stock, lemon juice, dried parsley, and red pepper flakes; let the sauce simmer gently for five minutes.
Remove the saucepan from heat and whisk in the remaining 8 tablespoons of butter until fully melted and the sauce is smooth; set aside.
Return the large pasta pot to the stove, add 1 tablespoon vegetable oil, and warm over medium heat.
Sauté the red, yellow, and green bell pepper strips along with sliced red onion until they begin to soften, about 3 to 5 minutes.
Add the drained pasta and prepared scampi sauce to the pot, tossing gently to coat the pasta without breaking it.
Adjust seasoning with salt and pepper to taste, adding reserved pasta water as needed to loosen the sauce.
Serve the pasta either in a large communal dish or divided plates, topped with freshly grated Parmesan if desired, then place the cooked chicken on top.
