Sauté the vegetables: Heat the olive oil in a large Dutch oven or pot 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.

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

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

To finish: 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.