Heat the olive oil in a medium pot or deep pan over medium heat.

Add the chopped onion and cook until softened, about 3-4 minutes.

Stir in the minced garlic and cook for another 1 minute until fragrant.

Add the diced potatoes and sliced carrots to the pot. Stir well to coat.

Pour in the chopped tomatoes and vegetable broth (or water). Add salt, black pepper, and dried oregano. Stir to combine.

Bring the mixture to a simmer, then reduce the heat to low, cover, and let it cook for 15-20 minutes, or until the potatoes and carrots are tender.

Gently stir in the drained tuna. Cook for another 5 minutes to allow the flavors to meld.

If using, stir in the fresh parsley, lemon juice, and red pepper flakes. Taste and adjust seasoning as needed.

Serve hot and enjoy your hearty stew!