How to Make It
Place carrots in a medium saucepan with water to cover, and bring to a boil over high. Reduce heat to medium, and simmer just until tender, 8 to 10 minutes. Drain and rinse with cold water; drain completely, and place in a large bowl.
Stir together vinegar, water, sugar, salt, onion powder, crushed red pepper, and mustard seeds in a medium saucepan, and bring to a boil over medium-high, stirring to dissolve sugar and salt. Pour hot liquid over carrots; cover and chill at least 4 hours or up to overnight.