How to Make It
Place beets in a pot, and add water to cover by 1 inch. Bring to a boil over high. Reduce heat to medium, and simmer until beets are tender, about 35 minutes. Drain beets. When cool enough to handle, rub skins off with a paper towel. Chill beets until cold.
Use a vegetable peeler or mandoline to cut carrots lengthwise into very thin strips. Cut beets into 1-inch pieces. Place carrots and beets in a medium bowl. Add lemon juice, salt, and gochugaru, and toss to combine. Cover and chill at least 1 hour. Add more lemon juice to taste before serving, if desired.