Heat oil and garlic in a small skillet over medium heat; cook 2 minutes, stirring occasionally. Remove from heat; cool slightly. Combine garlic mixture, 1 tablespoon nuts, vinegar, 1/4 teaspoon salt, pepper, and basil in a food processor; pulse until well combined.
Cook beans in boiling water 4 minutes or until crisp-tender; drain. Rinse under cold water; drain. Place in a large bowl. Add basil mixture and remaining 1/4 teaspoon salt; toss to coat. Sprinkle with 2 tablespoons nuts and tomatoes.