- 1 small sweet onion (such as Vidalia or Maui), thinly sliced
- 2 pounds medium pickling cucumbers, scrubbed, cut into 1/4-inch-thick rounds
- 1 large bunch dill, coarsely chopped (stems included)
- 1 tablespoon yellow mustard seeds
- 2 teaspoons whole white peppercorns
- 1 1/2 cups apple cider vinegar
- 1 cup water
- 1 cup sugar
- 3 tablespoons coarse kosher salt
- 2 teaspoons dill seeds
- Divide sliced onion between two 1-quart wide-mouth glass jars. Pack cucumber slices horizontally in jars. Top each jar with dill.
- Using mortar and pestle or resealable plastic bag and mallet, crush mustard seeds and peppercorns together. Place crushed spices in medium saucepan. Add vinegar, 1 cup water, sugar, coarse salt, and dill seeds. Bring mixture to boil over medium-high heat, stirring until sugar dissolves.
- Ladle mixture evenly over cucumbers. Leave jars uncovered and chill 24 hours. Cover glass pickle jars tightly with lids. DO AHEAD: Can be made 1 week ahead. Keep refrigerated.