Add lemon juice to apples and toss. Melt butter in a large skillet over medium high heat. Add apples, brown sugar, 1-1/2 teaspoons cinnamon, nutmeg and salt. Stir until well mixed and cook for 5 minutes, or until bubbly. Combine apple juice and corn starch in a small bowl; add to pan. Reduce heat to low, cover and simmer until apples are tender, 6 to 8 minutes. Remove apples from heat and chill for at least 2 hours.
Mix in chopped walnuts. Lay out a wonton wrapper. Scoop about 1 teaspoon of apple mixture into the center. Moisten two adjacent sides of the square with water and then fold the non moistened tip onto the moistened tip to form a triangle. Seal well, being sure to squeeze out air pockets. With the triangle facing down, moisten the left tip with water, and then bring the right tip under it, sealing the two together. Set onto a waxed paper lined sheet. Repeat with remaining filling and wrappers.
Mix sugar and remaining 2 teaspoons cinnamon, in a paper bag (lunch bag size).
Heat oil (about 2 to 3 inches deep) in a deep pan to 350°F. Fry a few wontons at a time until golden brown, 2 to 3 minutes. Remove from oil with a slotted spoon and place in paper bag. Shake the paper bag to evenly coat wontons. Remove from bag and serve warm. Continue to cook remaining wontons.