Preparation Cover beets generously with water in a heavy medium saucepan and simmer until tender when pierced in center with a knife, 30 to 45 minutes. Drain in a colander and cool to warm, then slip off skins. Cut beets into 1/4-inch slices. Meanwhile, whisk together vinegar, onion, sugar, 1/2 teaspoon salt, and 1/4 teaspoon pepper in a large bowl. Add oil in a slow stream, whisking, then add warm beets and parsley and toss. Season with additional sugar and salt. Serve warm or at room temperature. Cooks' note:Beets can be roasted and sliced 1 day ahead and chilled, covered. Bring to room temperature before tossing with vinaigrette and parsley.
Preparation Cover beets generously with water in a heavy medium saucepan and simmer until tender when pierced in center with a knife, 30 to 45 minutes. Drain in a colander and cool to warm, then slip off skins. Cut beets into 1/4-inch slices. Meanwhile, whisk together vinegar, onion, sugar, 1/2 teaspoon salt, and 1/4 teaspoon pepper in a large bowl. Add oil in a slow stream, whisking, then add warm beets and parsley and toss. Season with additional sugar and salt. Serve warm or at room temperature. Cooks' note:Beets can be roasted and sliced 1 day ahead and chilled, covered. Bring to room temperature before tossing with vinaigrette and parsley.