Combine 1/2 cup all-purpose flour and salt and pepper to taste on a plate or shallow dish.
Dredge each of the 8 chicken breasts in the flour mixture, coating both sides. Set the coated chicken aside.
Bring a large pot of salted water to a boil and cook 1 lb thin linguine according to the package instructions. Drain and keep warm.
In a large skillet, heat 1/2 cup olive oil and 2 tbsp butter over medium heat until the butter is melted and the oil shimmers.
Add the floured chicken breasts to the skillet and fry 3–4 minutes per side, until nicely browned. Work in batches if the skillet is too crowded. Transfer the browned chicken to a plate and set aside.
To the remaining oil and butter in the skillet, add 4 tsp minced garlic and 1 tsp onion powder. Cook briefly until fragrant (about 30 seconds), stirring so the garlic does not burn.
Pour in 3/4 cup chicken stock and cook 2–3 minutes, scraping any browned bits from the bottom of the skillet.
Add 43.5 oz crushed tomatoes and 1 tbsp sugar to the skillet. Season with additional salt and pepper to taste. Reduce heat to low and simmer, uncovered, for 25–30 minutes, stirring occasionally.
With about 5 minutes left in the simmer, stir in 1/4 cup freshly chopped parsley.
Nestle the browned chicken breasts into the sauce. Sprinkle 1 1/2 cups grated Parmesan cheese evenly over the chicken. Cover the skillet and cook until the cheese starts to bubble and the chicken is cooked through (no pink remaining).
To serve, divide the cooked linguine among plates, spoon sauce over the noodles, and place a chicken breast on top of each portion. Garnish with additional chopped parsley and extra Parmesan if desired.