In a 3.5 L Braiser or or 4.2 L Round Dutch Oven, heat half of the oil over medium heat. Add the onion and cook, stirring occasionally, until slightly browned. Add the garlic and red pepper flakes. Cook for 1 minute. Set aside in a bowl.
In the same Braiser or Round Dutch Oven, heat the remaining oil over medium-high heat. Add the eggplant and cook until browned on all sides, about 8 minutes. Add the bell pepper and cook over medium heat for 2 minutes to soften slightly. Add the tomato paste and harissa. Cook, stirring, for 1 minute. Add the onion mixture, cherry tomatoes, water, brown sugar and vinegar. Season with salt.
Cover and simmer gently over low heat for 1 hour, stirring occasionally, until the vegetables are very tender.
Stir in the lemon juice and adjust the seasoning. Serve warm or cold in a 380 ml Eggplant Casserole. Serve with fresh bread or crackers.