Melt butter in a large, deep nonstick skillet over medium heat. Add onion; cover and cook 3 minutes. Uncover and cook 10 minutes, stirring frequently. Add garlic; sauté 1 minute. Add Brussels sprouts; cover and cook 5 minutes or until crisp-tender. Remove from heat.
Combine vinegar and next 3 ingredients; add to Brussels sprouts mixture, tossing gently. Top with almonds.