Pre-heat the oven to 400°F.
Coat the tomatoes in EVOO and season with salt and pepper. Roast for 20 minutes to concentrate the flavor and burst the tomatoes.
Cut two large 1-inch-thick “planks” of bread by slicing the bread lengthwise horizontally. Reserve the rest of the loaf for another use.
When you remove the tomatoes from the oven, switch on the broiler. Char the bread on both sides, then rub the hot bread with the halves of garlic.
In a bowl, lightly mash the roasted tomatoes and combine with the scallions and basil. Top the large planks of bread with the tomato mixture, then cut each giant crostini into four pieces, for a total of eight pieces.