In a large pot, heat the olive oil over medium heat. Add the chopped onion and sauté for about 5 minutes until it becomes translucent. Stir in the minced garlic and cook for another minute until fragrant.
Add the chopped cabbage, diced carrots, diced celery, and diced bell pepper to the pot. Sauté the vegetables for about 5-7 minutes until they begin to soften.
Pour in the diced tomatoes with their juices and the vegetable broth. Stir in the dried thyme, dried oregano, red pepper flakes (if using), and season with salt and pepper to taste.
Bring the mixture to a boil, then reduce the heat to low and let it simmer for about 20 minutes, stirring occasionally.
After 20 minutes, add the green beans and frozen peas to the pot. Continue to simmer for an additional 10 minutes until all the vegetables are tender.
Stir in the fresh lemon juice and adjust seasoning if needed. Remove from heat and let it cool slightly before serving.
Serve hot, garnished with fresh parsley.