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.

Peppers are done when strips are tender, yield to a spoon, and have lightly browned or blistered edges — no mushiness, no raw crunch. Taste one before pulling the pan: it should be sweet and slightly caramelized. Serve immediately for best texture. Store covered in the fridge up to two days; bring to room temp or reheat gently before serving. Main mistakes: heat too high (scorches outside before inside softens) and overcrowding the pan (causes steaming, kills browning). Medium heat, give them space.