Slice each zucchini in half lengthwise to create 4 "steaks." Score the flesh side of each steak 1/4" deep diagonally at 1/2" intervals. Rotate the steaks 90° and score diagonally again to make a crosshatch pattern. Season the scored sides with 1 teaspoon of salt and let sit for about 15 minutes to allow the zucchini to release moisture.

Preheat your oven to 425°F and place a rack in the center. In a large skillet over medium heat, cook the garlic and red pepper flakes in 2 tablespoons of olive oil, stirring until fragrant, about 1 to 2 minutes. Transfer the garlic oil to a small bowl.

In the same skillet over medium-high heat, heat 1 tablespoon of olive oil. Pat the zucchini dry and place 2 halves flesh side down in the skillet, cooking until golden brown on the bottom, about 2 to 3 minutes. Transfer to a baking sheet flesh side up. Repeat with the remaining zucchini halves and 1 tablespoon of olive oil.

Brush the steaks with the garlic oil and bake until tender in the center, about 8 to 10 minutes. Top with mozzarella and Parmesan cheese.

Heat the broiler on high and broil the zucchini, watching closely, until the cheese is melted and browned, about 2 to 3 minutes.

Transfer the zucchini to a platter and top with fresh basil and more red pepper flakes if desired.