Begin by heating a generous splash of olive oil in a large skillet over medium heat. Add diced onion and minced garlic, stirring frequently until the onion becomes translucent and fragrant, about 3-5 minutes.

Next, sprinkle in the cayenne pepper along with your choice of other spices. Allow the spices to bloom in the oil for about 1-2 minutes, stirring constantly.

Pour in the diced tomatoes, mixing well to incorporate everything. Raise the heat slightly and bring the mixture to a gentle simmer, letting it cook for about 10 minutes.

Gently place your firm white fish into the sauce, ensuring it's coated evenly. Cover the skillet and simmer for 10-15 minutes, or until the fish is opaque and flakes easily with a fork.

Once the fish is cooked, taste the sauce and adjust the seasoning as needed.

To serve, plate the flaky fish and generously spoon the rich sauce over each piece. Garnish with a sprinkle of fresh herbs.