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.

Heat 2 tablespoons of 4 tbsp olive oil divided in a large Dutch Oven or heavy-bottomed Pot over medium-high heat. Add the 1 medium eggplant cut into 3/4-inch cubes in a single layer (work in batches if needed) and cook, stirring occasionally, until golden and slightly softened, about 6–7 minutes. Transfer to a plate and set aside.

Reduce the heat to medium. Add the remaining 2 tablespoons of 4 tbsp olive oil divided to the same Pot. Add the diced 1 yellow onion diced and cook, stirring frequently, until softened and translucent, about 5 minutes.

Add the 1 red bell pepper seeded and cut into 3/4-inch pieces and 1 yellow bell pepper seeded and cut into 3/4-inch pieces to the Pot. Cook, stirring occasionally, until they begin to soften, about 4 minutes.

Push the vegetables to the side and add the minced 4 cloves garlic minced to the center of the Pot. Cook, stirring constantly, for 1 minute until fragrant. Then stir everything together.

Add the 2 zucchini cut into 3/4-inch half-moons to the Pot and stir to combine with the other vegetables. Cook for 3 minutes, just until the 2 zucchini cut into 3/4-inch half-moons begins to soften slightly.

Return the sautéed 1 medium eggplant cut into 3/4-inch cubes to the Pot. Pour in the 1 can crushed tomatoes and add the fresh diced 1 can crushed tomatoes. Stir in the 1 tsp dried oregano, 1 tsp dried herbes de Provence (if using), 1 piece bay leaf, ½ tsp kosher salt plus more, ¼ tsp black pepper freshly ground, and 1 tsp sugar to balance acidity (if using). Stir everything together well.

Bring the mixture to a gentle boil, then reduce the heat to low. Cover the Pot with the lid slightly ajar and simmer for 30 minutes, stirring every 10 minutes, until all the vegetables are very tender and the flavors have melded together. The stew should be thick and fragrant.

Remove and discard the 1 piece bay leaf. Taste and adjust seasoning with ½ tsp kosher salt plus more and ¼ tsp black pepper freshly ground as needed. If the 1 can crushed tomatoes are very acidic, add a small pinch of 1 tsp sugar to balance acidity to balance.