1. Cook beans in boiling salted water to cover in a Dutch oven over medium-high heat 4 minutes or until crisp-tender. Plunge beans into ice water to stop cooking process. Drain; pat dry.
2. Sprinkle onion wedges with salt and pepper, and cook in 1 Tbsp. hot olive oil in a large cast-iron skillet over medium-high heat 3 minutes on each side or until charred and tender. Remove onions from skillet; wipe skillet clean.
3. Cook garlic in remaining 1 Tbsp. oil in skillet over medium heat 30 seconds or until fragrant. Add beans and thyme, and cook, stirring occasionally, 3 minutes or until beans are slightly charred. Stir in vinegar, next 3 ingredients, and onion wedges; toss to coat. Remove from heat; sprinkle with salt and pepper. Serve hot.