How to Make It
Preheat the oven to 350°. In a medium bowl, whisk together 1/4 cup of the raspberry vinegar, 1 1/2 tablespoons of the honey, the shallot, 1/2 teaspoon of salt and 1/2 teaspoon of pepper. Whisk in the grapeseed oil until emulsified.
Arrange the beets so they fit snugly in a single layer in a deep baking dish. Add enough water to barely cover the beets, then add the remaining 1/4 cup of vinegar and 1 1/2 tablespoons of honey and the butter. Season with salt and pepper. Cover with foil and bake for 50 to 60 minutes, or until the beets are tender when pierced with a knife. Let cool slightly.
Drain and peel the beets and slice them 1/4 inch thick. Add them to the honey dressing and let cool for up to 4 hours.
To serve, arrange half of the beet slices on 8 small plates and cover with the feta. Top with the remaining beet slices and drizzle each serving with about 1 tablespoon of the dressing. Garnish with the greens and serve.