Preheat oven to 475 degrees F. Set a sauce pan over medium heat. Add 1 tablespoon of olive oil, onions, and anchovies. Sauté for 2 minutes, then add the garlic, tomatoes, and tomato paste. Salt and pepper to taste.
Bring the mixture to a boil and reduce heat to a simmer. Simmer 10-15 minutes.
Meanwhile, pat the fish dry with a paper towel. Then lightly oil, salt and pepper on both sides. Roast on a rimmed baking sheet for 6-8 minutes, depending on the thickness of the fish.
Brush the bread with olive oil and toast in the oven for 3-5 minutes. *You could put them on a lower rack with the fish to save time!
Stack the basil leaves. Roll them into a tight cylinder. Slice them thin into fine ribbons.
To assemble the bruschetta, top each bread slice with a fish fillet. Then add tomato sauce and sprinkle fresh basil ribbons over the fish. Serve immediately.