Heat a large pot over medium heat and add 1 tablespoon of olive oil. Once the oil shimmers, toss in the diced onion, minced garlic, green bell pepper, and sliced celery. Sauté these aromatics for about 5 minutes, stirring occasionally, until they soften and become fragrant.

Stir in 1 teaspoon of Cajun seasoning, ½ teaspoon of smoked paprika, ½ teaspoon of salt, and ¼ teaspoon of black pepper into the pot. Blend the flavors well, then add 1 cup of diced tomatoes, followed by 4 cups of fish or vegetable broth. Increase the heat to bring the mixture to a gentle simmer.

Carefully add 1 pound of white fish fillets cut into bite-sized chunks to the simmering broth. Allow the fish to cook for 5 to 7 minutes, gently stirring occasionally until the fish turns opaque and flakes easily with a fork.

Ladle the hot soup into bowls, serve optionally over 1 cup of cooked rice for added heartiness. Garnish each bowl with freshly chopped parsley or green onions.