In a medium skillet over medium-low heat, heat oil. Add garlic and cook, stirring occasionally, until lightly golden, 2 to 4 minutes. Let cool.
Meanwhile, set a large strainer or colander over a bowl. Add tomatoes and toss with ½ tsp. salt. Let sit 5 minutes.
Transfer tomatoes to a large bowl. Add basil, vinegar, red pepper flakes, and ½ tsp. salt and toss to combine. Add garlic and oil from skillet and toss again to combine. Let marinate at least 30 minutes and up to 2 days.
Arrange a rack in center of oven; preheat to 400°. Brush bread on both sides with oil and arrange on large baking sheet.
Toast bread, turning halfway through, until dried and golden brown, 10 to 15 minutes. Let cool 5 minutes, then rub one side of bread with halved garlic cloves.
Arrange bread on a platter. Spoon tomatoes on garlic-rubbed side of bread just before serving.
