Trim, peel and halve 2 1/2 pounds medium beets; slice as directed (see left). Place the beets in a 9-by-13-inch baking dish and drizzle with 3/4 cup olive oil; season with 1/4 teaspoon salt and a few grinds of pepper. Add cup water and cover with foil. Roast at 425 degrees F, 40 minutes. Uncover and continue roasting, spreading the slices apart and basting with the pan juices halfway through, until the beets are tender, 30 to 40 more minutes. Let cool slightly. Mix 1/2 cup plain Greek yogurt with 2 tablespoons each chopped dill and lemon juice, 1 teaspoon salt and a few grinds of pepper. Drizzle over the beets and top with crushed pink peppercorns and more dill.
Cut a thin sliver from one side of the vegetable so it can sit flat. (If you¿re starting with halved veggies, like the beets at right, skip this step.)
Position the vegetable cut-side down between the handles of two wooden spoons.
Using a sharp knife, make crosswise cuts (1/8 to 1/4 inch apart), stopping when the knife hits the handles so you don't cut all the way through the vegetable.