Cook the noodles in boiling salted water one to two minutes less than the package recommends, drain and set aside.
In a small bowl mix the crushed crackers and melted butter. Set aside.
While the pasta cooks, melt 1 tablespoon of butter in a large skillet over medium heat. Add the celery, onion, peas, and garlic and saute until the celery starts to soften (about 3 to 4 minutes). Remove vegetables to a plate and set aside.
Add the remaining 3 tablespoons butter to the pan over medium heat and let it melt. Add the flour and cook, stirring constantly for 30 seconds. Add chicken broth and milk, whisking constantly until smooth, thickened and bubbly; about 2-3 minutes. The mixture should coat the back of a spoon.
Turn off the heat and add salt, lemon juice, parsley, and ½ cup of the parmesan cheese. Taste the sauce and season with additional salt, pepper, or lemon juice, as needed.
Stir in the egg noodles, sauteed vegetables and tuna, stirring gently to combine so you don’t break the tuna up too much.
Pour the mixture into a 9x13’’ or similar size baking dish. Sprinkle with remaining ½ cup parmesan cheese.
Add the crushed crackers on top.
Bake at 350 for 25-30 minutes.