Quick-pickled radishes with red onions add a tangy crunch to dinner, cheese plates, charcuterie boards, or avocado toast!
In a saucepan over medium-high heat, boil water, sugar, and salt until dissolved.
Add vinegar, then remove from heat. Divide red onion and radish between two jars, add black pepper, and pour in hot vinegar to cover. Seal and shake briefly.
Let cool for 1 hour, then refrigerate.