Heat olive oil in a large pot over medium heat.
Add minced garlic and sauté until fragrant.
Add chopped bell pepper and cook until softened.
Pour in the vegetable broth and bring to a boil.
Carefully add the peeled onions to the broth.
Stir in diced tomatoes, salt, and black pepper.
Reduce heat to low and cover the pot.
Simmer for 25-30 minutes until onions are tender.
Taste and adjust seasoning as needed.
Serve hot, garnished with fresh herbs.