Bring 1/2 cup water, 2/3 cup vinegar, and 2 teaspoons honey to a boil in a small saucepan over high heat. Add onion; cook 1 minute. Remove pan from heat, and let stand until ready to use.
Meanwhile, whisk together oil, pepper, salt, remaining 2 tablespoons vinegar, and remaining 1 teaspoon honey in a large bowl. Add cabbage and parsley; toss to coat. Let stand 10 minutes.
Drain onions; stir into cabbage mixture.