This gratin is rich with aroma and flavor. It’s great for dinner served with a mixed greens salad topped with roasted red peppers and olives.
Bring a large pot of water to a boil. Slice potatoes 1/4-inch thick. Peel celery root; slice in quarters and then cut quarters into 1/4-inch slices.
Add salt to taste to boiling water, then add potatoes and cook until just tender, about 5 minutes. Using a slotted spoon, remove potatoes to a bowl, then add celery root to boiling water and cook until just tender, about 4 minutes. Using a slotted spoon, remove celery root to bowl with potatoes. Reserve cooking liquid.
In medium skillet, heat oil over medium heat. Add onion, garlic, celery and basil and season to taste with salt and pepper. Cook, stirring often, until softened, about 5 minutes. Add wine, increase heat and cook to reduce wine by half, about 5 to 7 minutes. Add tomatoes and their juices plus 1/2 cup of reserved cooking liquid.
Preheat oven to 375F. Grease a 2- quart baking dish. Ladle half of the tomato mixture in bottom of prepared pan. Make a layer of alternating potato and celery root slices, season to taste with pepper. Repeat, using remaining potato and celery root slices. Cover with remaining tomato mixture. Cover and bake until potatoes and celery root are tender, about 45 minutes. Remove gratin from oven and let stand 10 minutes before serving. Serve warm.