Heat the olive oil in a large pot over medium heat. Add the diced onion and cook for 5 minutes until it softens.
Stir in the minced garlic, ground cinnamon, and dried oregano. Cook for 1 minute until the garlic smells fragrant.
Pour in the crushed tomatoes and fish stock. Add the salt and black pepper, then bring the mixture to a gentle simmer.
Lower the heat and let the stew bubble slowly for 10 minutes so the flavors blend.
Place the sea bass fillets into the simmering liquid. Cover the pot and cook for 8 to 10 minutes until the fish flakes easily with a fork.
Sprinkle the chopped parsley over the stew right before serving. Offer lemon wedges on the side.