Preheat oven to 450°F (230°C). Lightly oil a baking sheet or line with parchment paper and lightly oil. Place sliced tomatoes in a single layer on baking sheet and sprinkle with salt and pepper. Bake for 20 minutes or until tomatoes are slightly roasted and soft.

Meanwhile, cook beans in a large saucepan of boiling salted water until tender crisp, about 5 minutes. Drain and plunge into a bowl of ice water to chill. Drain. Pat dry with paper towels. Arrange on a serving platter just large enough to hold them.

Combine remaining ingredients in a bowl. Whisk to blend.

When tomatoes are baked, remove from oven. Slightly cool, then, purée in a blender or food processor just until coarsely chopped. Spoon over centre of green beans. Drizzle with dressing. Cover with plastic wrap and refrigerate until ready to serve. Salad can be made the evening ahead.