Melt the butter in a saucepan over medium-high heat. Add shallots; sauté 4 minutes or until golden. Stir in vinegar; cook 1 1/2 minutes. Remove from heat. Stir in thyme, rind, salt, and pepper.
Cook beans in boiling water 3 minutes or until crisp-tender; drain. Place beans in a large bowl. Stir in shallot mixture; toss well to coat.