Bread-and-Butter Pickles

INGREDIENTS

• 1 English cucumber or 6 pickling cucumbers (about 1 lb.)
• 1 white onion, thinly sliced
• 2 cups white wine vinegar
• 3/4 cup sugar
• 1/4 cup kosher salt
• 1 tsp. celery seeds
• 1 tsp. mustard seeds
• 2 bay leaves