Heat the oil in a large stockpot over medium heat and sauté the onions and celery until soft, 6 to 7 minutes. Set aside. In the same stockpot over medium heat, add the ground beef and cook, stirring to break up the meat, until evenly browned, 5 to 7 minutes. Return the onions and celery to the pot and add the water chestnuts, mushrooms, tomato puree, and sugar; simmer for 20 minutes, stirring occasionally. Add salt and pepper to taste and stir in the lemon juice. Stir in the cooked noodles and a third of the Cheddar cheese.

Preheat the oven to 350°F. Spoon the casserole mixture into a greased 3-quart baking dish or baking pan. Top with the remaining cheese. Bake, uncovered, until bubbling, about 45 minutes. If needed, brown under the broiler for a few more minutes. Remove from oven and let rest for 5 to 10 minutes before serving.