Rinse peppers under cold water and pat dry. Slice off tops and bottoms, stand upright, and cut down along the inside to remove seeds and white ribs. Slice lengthwise into ½-inch strips; halve crosswise for shorter pieces. Keep sizes uniform so everything cooks evenly. If adding onion, slice it now. Measure out olive oil, salt, and pepper. Have everything ready before the pan goes on — sautéing moves fast.

Heat a large Skillet over medium heat. Add 1 tbsp olive oil per 2 peppers; warm 30–60 seconds until shimmering. Add pepper strips in a single layer — work in batches if crowded. Season with salt and pepper, stir to coat. Cook over medium heat, stirring every 2–3 minutes, for 6–10 minutes. At 6 minutes: slightly softened with snap. At 10 minutes: tender throughout with light color. For very soft peppers, cook 30–40 minutes over medium-low, stirring occasionally. Add garlic halfway through cooking. If browning too fast, add a splash of white wine or water and briefly cover to steam.

Pat 1 ½ lb boneless skinless chicken breasts pounded to even thickness dry and season both sides with ½ tsp garlic powder, ½ tsp onion powder, ½ tsp salt, and ¼ tsp black pepper freshly ground. Heat 1 tbsp olive oil in a large Skillet over medium-high heat. Add 1 ½ lb boneless skinless chicken breasts pounded to even thickness and cook for 5–6 minutes per side until golden and cooked through (internal temp 165°F). Transfer to a Cutting Board, rest for 5 minutes, then slice into strips.

Add the drained 1 cup raw cashews soaked in hot water for 15 minutes, then drained, 1 ½ cups unsweetened plain oat milk or other unsweetened dairy-free milk, ½ cup low-sodium chicken broth, minced ½ tsp garlic powder, 3 tbsp nutritional yeast, 1 tbsp lemon juice freshly squeezed, ½ tsp salt, and ¼ tsp white pepper or black pepper to a Blender. Blend on high for 60–90 seconds until completely smooth and creamy.

In the same Skillet used for the 1 ½ lb boneless skinless chicken breasts pounded to even thickness (wiped clean), melt the 1 tbsp dairy-free butter such as Earth Balance or Miyoko's over medium heat. Pour in the blended 1 cup raw cashews soaked in hot water for 15 minutes, then drained sauce and stir constantly for 3–4 minutes until the sauce thickens slightly and is heated through. If it becomes too thick, stir in reserved pasta water a splash at a time until you reach a silky, coating consistency. Taste and adjust ½ tsp salt as needed.

Add the drained 12 oz fettuccine or linguine to the Skillet with the sauce and toss with Tongs until every strand is well coated. Divide among bowls, top with sliced 1 ½ lb boneless skinless chicken breasts pounded to even thickness, and garnish with 2 tbsp fresh parsley chopped and dairy-free parmesan store-bought, for serving if desired. Serve immediately.