1) Preheat the oven to 200C/Gas 6.
2) Coat the tomatoes in olive oil and season with salt and pepper. Roast for 20 minutes to concentrate the flavour and burst the tomatoes.
3) Cut two large planks of bread, each 2 1/2-cm thick, by slicing the bread lengthwise horizontally. Reserve the rest of the loaf for another use.
4) When you remove the tomatoes from the oven, switch on the grill. Char the bread on both sides then rub the hot bread with the cut garlic.
5) In a bowl, lightly mash the roasted tomatoes and combine with the spring onions and basil.
Top the large planks of bread with the tomato mixture then cut each plank into four pieces, eight pieces in total.