This chef recipe is from Chef Daniel Alvarez of 606 Congress in Boston. You can use the same method for other vegetables such as beets.
1 head cauliflower, cut into florets
1 quart white vinegar
1/4 cup kosher salt
1/4 cup sugar
3-4 sprigs fresh thyme sprigs
1-2 cloves garlic
6 ounces water (if needed)
1. Place cauliflower in a jar or airtight container(s). Set aside.
2. Place vinegar, salt and sugar in a saucepan and bring to a boil. Remove from heat when sugar and salt have dissolved.
3. Pour liquid over cauliflower and add garlic and thyme and cover container (if mixture seems too strong add some water to dilute). Allow to sit at least 48 hours before serving (will keep in refrigerator for up to 1 month).