Add asparagus and dill into a 32-ounce mason jar. Set aside.
In a medium saucepan, combine the vinegar, water, granulated sugar, kosher salt, pickling seasoning, and red pepper flakes. Bring to a simmer over medium heat and stir until the sugar and salt are dissolved, about 1 minute.
Once the sugar has dissolved, remove the pan from the heat and carefully pour the liquid over the asparagus in the jars, filling to the top. Make sure the brine completely covers the asparagus.
Allow the jars to cool to room temperature, then cover and refrigerate for at least 48 hours before eating.
Notes
Serve the pickled asparagus as a side dish or appetizer.
These pickles will last in the fridge for 2-3 weeks.
If you find the brine does not cover your asparagus in the jars, add equal parts of water and vinegar until all the asparagus is covered.