Start by slicing each zucchini lengthwise into halves, then use a spoon to carefully scoop out the flesh, leaving about a quarter-inch border to maintain the shell's structure. Set the scooped flesh aside for other uses or discard.
Brush the hollow zucchini shells generously with olive oil on all sides, then sprinkle inside with salt and pepper to season thoroughly. This helps prevent sticking and enhances flavor.
Preheat your grill to medium-high heat until it’s hot enough to sizzle when the flesh hits the grates. Place the zucchini flesh side down and listen for that satisfying sizzle and slight crackle as they start to char.
Grill the zucchini shells flesh side down for about 3-4 minutes, until you see nice grill marks and a caramelized surface. Use tongs to flip them gently and cook the other side for another 2-3 minutes until tender but still holding their shape.
While the zucchini grills, combine the chopped tomatoes, grated Parmesan, and chopped basil in a bowl. Mix well to create a fresh filling mixture.
Once the zucchini shells are grilled, carefully spoon the tomato and cheese mixture into each boat, pressing gently to pack the filling in without spilling.
Return the filled zucchini boats to the grill for an additional 2-3 minutes, just to warm the filling and let the flavors meld. If desired, sprinkle with breadcrumbs or extra cheese at this stage for added crunch.
Remove the zucchini from the grill once the filling is heated through and the tops are slightly golden. Let them rest for a minute, then serve hot, garnished with additional basil if desired.
