Heat the olive oil in a large Dutch oven over medium heat. Add the onions, carrots, celery, and tomato paste. Cook, stirring often, until the vegetables have softened and the onions are translucent, 8 to 10 minutes.

Stir in the garlic, fennel, black pepper, ½ teaspoon of salt, and the red pepper flakes. Cook, while stirring, for one minute.

Pour in the canned tomatoes and their juices and the stock/broth. Add the potatoes, cabbage, and bay leaves. Raise the heat to medium-high and bring the soup to a boil. Partially cover the pot with a lid, then reduce the heat to maintain a low simmer.

Simmer for 20 minutes or until the potatoes and other vegetables are tender. Add the frozen peas and cook for five more minutes.

Remove the pot from the heat and remove the bay leaves. Stir in the cider vinegar (or use lemon juice). Taste and season with more salt, pepper, or vinegar. Serve.