- Preheat oven to 350 degrees. Place sunchokes in a wide bowl and fill with water. Scrub skins of sunchokes with a vegetable brush under running water to remove any dirt, then drain. Replace water in the bowl and wash sunchokes one more time. Wash turmeric root in the same water, then pour the water out. Using a mandoline or a sharp knife, slice cleaned sunchokes and turmeric into 1/16-inch slices. Place them in a clean bowl and set aside.
- On a cutting board, slice the two lemons in half lengthwise, through the stem end. Place each lemon half cut side down and, using a sharp knife, cut lemons as thinly as possible while still leaving them whole slices. Remove seeds. Add lemons to sliced vegetables. Season with salt and pepper and toss well to incorporate. Transfer ingredients to a wide, shallow casserole dish or rimmed baking pan that snugly holds the contents. Add olive oil and toss well.
- Place pan in center rack of oven and bake for 35 to 40 minutes or until sunchokes are tender and edges of vegetables are slightly browned. Transfer to serving dish and garnish with fresh mint and more black pepper. Serve warm or at room temperature.