Rinse tomatoes and pat dry. Heat olive oil over medium heat. When hot, add tomatoes and stir 3 minutes. Add garlic and salt, stirring 1 minute. Remove pan from heat and spoon tomatoes into a bowl.
Off the heat, stir arugula in hot pan just until almost wilted. Add to tomatoes and season with pepper and vinegar, stirring gently to mix. Serve warm or at room temperature.