Top yogurt with beets and sliced grapefruit, then tarragon, toasted pine nuts, and
reserved grapefruit zest.
Arrange beets on a platter; drizzle with more oil and top with fried rosemary and
reserved grapefruit zest.
Transfer to a large bowl and gently mix in cream, milk, salt, and
reserved grapefruit zest; let sit 5 minutes.