Prepare the Jerusalem Artichokes: Scrub the artichokes well to remove any dirt. If some are significantly larger than others, cut them into smaller pieces to ensure even cooking.
Preheat the oven to 220°C/430°F (static)
Boil Until Just Tender: Place the Jerusalem artichokes in a pot of cold, salted water and bring to a boil. Simmer for about 15-20 minutes, or until they are soft enough for a knife to go through easily but not falling apart. They need to be still firm as we need to cut them. Drain and let them cool slightly.
Roast to Perfection: Cut the Jerusalem artichokes in half and place them cut-side down on a oiled baking tray. Drizzle with olive oil, sprinkle with salt, and scatter fresh rosemary over them. Brush the oil to make sure they are well coated.
Crisp Them Up: Roast them in the middle rack for 25 minutes, then place the tray on the bottom rack of the oven to help them get a deep golden crust for another 20 minutes or so (check by lifting a few and see if they are caramelizing)
Make the Tahini Yogurt: While the artichokes are roasting, mix the plant-based yogurt with tahini in a bowl until smooth. Adjust with salt.
Assemble the Dish: Spread the tahini yogurt onto a serving plate. Arrange the roasted Jerusalem artichokes on top, and finish with a sprinkle of lemon zest for freshness. Serve warm and enjoy!