Preheat a grill or grill pan over medium-high heat.
Pat the swordfish steaks dry with paper towels and season both sides with salt and freshly ground black pepper.
Brush the swordfish with 1 tablespoon of olive oil, ensuring both sides are well coated.
Place the swordfish steaks on the grill and cook for about 4 to 5 minutes on each side, or until the fish is cooked through and grill marks appear.
While the swordfish is grilling, heat the remaining olive oil in a skillet over medium heat.
Add the minced garlic to the skillet and sauté until fragrant, about 1 minute.
Stir in the cherry tomatoes and cook until they start to soften, about 3 minutes.
Add the sliced olives, capers, and lemon zest to the skillet, and cook for an additional 2 minutes.
Remove the skillet from the heat, stir in the chopped basil and lemon juice, and season with salt and pepper to taste.
Once the swordfish steaks are done, transfer them to a serving platter.
Top the grilled swordfish with the cherry tomato and olive mixture.
Garnish with additional fresh basil leaves before serving.