Peel the zucchini. Cut into quarters lengthwise, then remove seeds and cut crosswise (as you would cut apples for apple pie). Toss together 4 cups chopped zucchini, lemon juice and salt. Place mixture into frying pan and cook until tender-crisp.
In a separate bowl, mix together the brown sugar, cinnamon, cream of tartar, nutmeg and flour. Add the cooked zucchini to sugar mixture and mix well. It will be a little runny, but that's OK.
Place filling into a 9 inch pie crust, dot with butter, and place top crust on. Bake in oven at 400 degrees F (205 degrees C) for 40 minutes or until golden brown.