Pickled Pepper and Onion Relish

1. Prepare the Vegetables:
   • Slice the bell peppers and red onion thinly.
2. Make the Pickling Liquid:
   • In a medium saucepan, combine the vinegar, water, sugar, salt, garlic, mustard seeds, black peppercorns, and crushed red pepper flakes (if using).
   • Bring the mixture to a boil over medium heat, stirring occasionally to dissolve the sugar and salt.
3. Pack the Vegetables:
   • While the pickling liquid is heating, pack the sliced peppers and onions into a clean jar or several smaller jars.
4. Add the Pickling Liquid:
   • Once the pickling liquid has come to a boil, pour it over the packed vegetables in the jars. Make sure the vegetables are fully submerged.
5. Cool and Refrigerate:
   • Let the jars cool to room temperature.
   • Once cooled, seal the jars with lids and refrigerate. The relish will be ready to eat in about 24 hours, but it will develop more flavor after a few days.
6. Serve:
   • Use the relish as a topping for burgers, sandwiches, hot dogs, or as a side to grilled meats.

Enjoy your homemade pickled pepper and onion relish!