How to Make It
Preheat the oven to 425°. In a medium enameled cast-iron casserole, cover the beets with water and bring to a boil. Cover and braise in the oven for about 2 hours, until very tender. Using a slotted spoon, transfer the beets to a cutting board. When cool enough to handle, slip off the skins. Cut the beets into 1-inch pieces, spread them on a baking sheet and refrigerate until cold, about 1 hour.
In a food processor, combine the braised beets with the garlic, coriander and lemon juice and pulse until finely chopped. With the machine on, slowly drizzle in the olive oil until incorporated and the beet puree is smooth. Scrape into a bowl and whisk in the tahini. Season with salt and serve with pita bread.