Created by lazyme on March 13, 2015
Step 1: Put oven rack in middle position and preheat oven to 450°F.
Step 2: Oil a 13- by 9-inch baking pan.
Step 3: After peeling onions, trim root ends, leaving onions whole, then quarter onions lengthwise.
Step 4: Put onions in baking pan, then drizzle with oil and vinegar, tossing to coat.
Step 5: Arrange onions with a cut side down and sprinkle with salt and pepper.
Step 6: Roast, uncovered, turning over once and basting with pan juices twice during baking, until deep golden, about 30 minutes.
Step 7: Add water to pan and roast until onions are tender and caramelized, about 20 minutes more.
Step 8: Transfer onions with pan juices to a large bowl.
Step 9: While onions are roasting, cook beans in a 5- to 6-quart pot of boiling salted water, uncovered, until crisp-tender, about 5 minutes.
Step 10: Drain beans in a colander, then add to onions and toss.
Step 11: Season with salt and pepper.