Slice each zucchini lengthwise to create 4 steaks. Score the flesh side in a crosshatch pattern. Sprinkle with salt and let rest for 15 minutes to release moisture.

Heat 2 tablespoons olive oil in a large skillet over medium heat. Add garlic and red pepper flakes. Cook for 1–2 minutes until fragrant. Transfer mixture to a small bowl.

Heat 1 tablespoon olive oil in the skillet. Pat zucchini dry, then place 2 halves flesh side down. Cook for 2–3 minutes until golden. Transfer to a baking sheet. Repeat with remaining zucchini and 1 tablespoon olive oil.

Brush seared zucchini with garlic oil. Bake in a preheated oven at 425°F (220°C) for 8–10 minutes, until tender.

Sprinkle mozzarella and Parmesan evenly on top. Switch to broil and cook for 2–3 minutes, until cheese is melted and browned.

Transfer to a platter, top with torn basil, and finish with extra red pepper flakes if desired.