Ingredients:
- 1 lb Persian cucumbers, thinly sliced
- 1 small red onion, thinly sliced into half-moons
- 1 cup apple cider vinegar
- 1/2 cup granulated sugar
- 1 tbsp kosher salt
- 1 tsp yellow mustard seeds
- 1/2 tsp celery seeds
- 1/2 tsp whole black peppercorns
Instructions:
- Pack the thinly sliced cucumbers and red onions into a clean quart-sized glass jar. Press them down firmly with your hand to ensure they are tightly packed and will stay submerged.
- Combine apple cider vinegar, granulated sugar, kosher salt, mustard seeds, celery seeds, and peppercorns in a small saucepan.
- Place the saucepan over medium heat and stir constantly until the sugar and salt have completely dissolved. Bring to a gentle simmer, then remove from heat immediately.
- Slowly pour the warm brine over the cucumbers and onions, filling the jar to the top while leaving about 1/4 inch of headspace.
- Stir gently with a butter knife to release trapped air bubbles, seal the lid tightly, and refrigerate for 24 hours for full flavor development.