BEET PUREE: Place beet in a small saucepan, and add enough water to cover by a ½ inch. Salt water, and bring to a boil. Reduce heat and simmer for 15 to 18 minutes, until the beet is tender and easily pierced with the tip of a paring knife. Drain and rinse under cool water. When the beet is cool enough to handle, peel, chop into 1-inch pieces, and place in a food processor. Add yogurt, oil, sesame seeds, thyme, pepper flakes, and salt, and blend until smooth. Taste and adjust seasoning as needed. Set aside.