Ingredients
2 tablespoons coriander seeds
1 tablespoon mustard seeds
3 medium red onions, cut in half lengthwise and thinly sliced
1/4 cup red-wine vinegar
1/4 cup white balsamic vinegar
1/8 cup sugar
3 fresh bay leaves
3 sprigs fresh thyme
Coarse salt and freshly ground pepper
1 tablespoon extra-virgin olive oil
Preparation
Toast the coriander seeds in a small, dry skillet over medium heat until fragrant, about 2 minutes. Add mustard seeds, and toast 1 minute more; set aside.
Soak onions in a large bowl of ice water, about 10 minutes. Drain, pat dry, and transfer to a medium heatproof bowl.
Place vinegars, sugar, bay leaves, and thyme in a small saucepan and slowly bring to a boil over medium heat; add reserved coriander and mustard seeds. If mixture seems too acidic, add a little water. Pour mixture over onions and let stand 5 minutes. Drain, discarding liquid, and season onions with salt and pepper.
Toss onions with olive oil and store, refrigerated, in an airtight container until ready to use, 2 to 3 weeks.