Sauteed Green Beans with Garlic

Heat olive oil in a 10-inch saute pan over medium-high heat. Add onion and cook until it starts to become translucent, 2 to 3 minutes. Add garlic and saute for 1 minute. Add vinegar and scrape and stir the brown bits from the pan.

Add green beans, butter, red pepper flakes, salt, and pepper; toss several times to mix with onions and garlic. Cook until beans are heated through and just start to lose their bright green color, about 5 minutes. Serve immediately.