Cut off all but 2-inches of the beet tops, leave the root ends attached. Peel and slice the onions into 1/4-slices. Heat enough water to cover beets to boiling. Add beets and 2 t vinegar for each quart of water used. Cover and heat to boiling. Cook until beets are tender, 35 to 45 minutes; drain. Run cold water over beets, slip off skins and remove the root ends. Cut beets into 1/4-inch slices. Heat remaining ingredients to boiling in a 6-quart Dutch oven, reduce heat. Simmer, uncovered 10 minutes, stir in beets. Pack beets and onions in hot jars, leaving 1/2-inch head space. Heat syrup to boiling. Pour over beets and onions, leaving about 1/2-inch head space; seal. Process 30 minutes in boiling water bath. Makes about 8 Pints.
NOTE: 7 cans (16 ounces each) sliced beets, drained, can be substituted for the beets in the above recipe.