Preheat the oven to 450°F and line a baking sheet with parchment paper.
Combine the olives, basil leaves, olive oil, rinsed capers, minced garlic, and lemon zest in the bowl of a food processor.
Pulse the mixture until it forms a coarse paste, scraping down the sides as needed; add a little more olive oil if the mixture is too dry.
Place the fish fillets on the prepared baking sheet and season them lightly with freshly ground black pepper.
Evenly spread the tapenade over the top of each fillet, dividing it among the four pieces.
Bake the fillets in the preheated oven for about 15–17 minutes, or until the fish is cooked through and flakes easily with a fork; cook time will vary with thickness.
Let the fish rest for 3 minutes, then finish with additional freshly ground black pepper if desired.
Serve hot with fresh lemon wedges and an optional drizzle of extra olive oil.