Apples are at their peak for eating out-of-hand at harvest time, but their staying qualities make them good for cooking in all seasons and there are desserts to fit all seasons.

Unlike most fruits, the apple comes in many varieties. There are shapes, colors, textures and flavors to suit all tastes and to meet the most varied demands. The encyclopedia says the ancient Romans had developed 22 varieties and that in 17th-century France, 56 different kinds were known.

Today there are more than 6,000 varieties throughout the world. For our purposes, the 15 or so varieties that surround us are quite sufficient. For cooking, I would recommend the Stayman Winesap, Jonathon, Northern Spy, Golden Delicious and, for use in a soft or meaty sauce, the MacIntosh. That leaves the Gravenstein, York Imperial. Starr, Grimes Golden, Greening, Pippen, Rome Beauty, Baldwin, crab apple and the Red Delicious. CALVADOS CUSTARD APPLE TARTE

(1 tart)

The name is not as impressive as the tart itself. Just by pouring a calvados - or brandy - custard over the apples in the shell you make a sensationally different tart. It is at its best served piping hot, but is good at any temperature. 1 partially baked pastry shell (in 8- or 9-inch tart pan) 2 or 3 large tart apples, peeled, cored and cut into 1/8-inch slices (about 3 cups) 2/3 cup sugar 1/2 teaspoon cinnamon 1 egg 3 tablespoons flour 1/2 cup heavy cream 1/3 cup Calvados or brandy

Mix apple slices with 1/3 cup sugar and cinnamon. Arrange in the partially baked shell and bake at 375 degrees for 20 minutes or until apples are almost tender. Beat egg until thick and creamy, then mix in remaining sugar and flour. Stir in cream and Calvados. Remove tarte from oven and pour liquid over the apples. Return to oven and continue to bake for 20 minutes or until custard is set and the top is nicely browned. May be made in advance. APPLE CRUNCH (6 to 8 servings)

Very quick and easy to prepare. May be made a day or two in advance and it freezes well. 6 to 8 tart apples, peeled, cored and sliced 1/3 cup brown sugar 1 teaspoon cinnamon Dash nutmeg 1 cup flour 1 cup granulated sugar 1 teaspoon baking powder 1/4 teaspoon salt 1 egg, beaten

Grease an 8-inch cake or pie pan and arrange sliced apples in it. Sprinkle with brown sugar, cinnamon and nutmeg. Sift together flour, granulated sugar, baking powder and salt. Add the egg and mix with a fork until crumbly. Spoon the batter over the apple slices and shake the pan a bit so it settles down. Bake at 350 degrees for 40 minutes, or until the apples test tender to a fork. Some apples cook faster than others so testing is necessary. This may be served either hot or cold, but as with most apple desserts it is better hot. Whipped cream or ice cream is an optional topping. SADIE'S APPLESAUCE CAKE (6 to 12 servings)

A moist spicy cake with great staying power, will keep up to a week in the refrigerator or can be frozen for still later use 1/2 cup butter 1 cup sugar 2 eggs, well beaten 1 1/2 cups unsweetened applesauce or unsweetened canned applesauce 1 teaspoon vanilla 2 cups flour 1 teaspoon cinnamon 2 teaspoon cocoa 1/2 teaspoon ground cloves 1/4 teaspoon salt 3/4 cup raisins 3/4 cup chopped walnuts or pecans 1/2 cup hot water 2 teaspoons baking soda

Cream together butter and sugar, then stir in beaten eggs applesauce and vanilla. Sift together flour, cinnamon, cocoa, clove and salt. Add raisins and nuts to flour mixture. Mix hot water and soda together. Stir the flour mixture and the hot water and soda alternately into the creamed mixture, with the flour as the last addition. Beat well. Pour into a greased loaf pan 12-by-8-by-2-inches. Bake at 375 degrees for 45 minutes. Test with a toothpick for doneness. Pick must come out clean. While still warm cover with the following icing. CAKE ICING 1/2 cup brown sugar 4 tablespoons heavy cream 1 tablespoon butter 1 cup grated coconut

Bring sugar, cream and butter to the boiling point in a saucepan. Off the heat, mix in coconut. Spread evenly on cake and put under a hot broiler until brown. AMSTERDAM APPLE TORTE (6 to 8 servings)

The appearance of this dessert belies the ease and quickness of its preparation. It may be made as much as two days in advance and it freezes well. 2 eggs 1/4 teaspoon salt 1 1/2 cups sugar 2 cups coarsely chopped apples, peeled and cored 1/2 to 1 cup chopped nuts 4 tablespoons flour 2 1/2 teaspoons baking powder 1 teaspoon vanilla

Cream together until smooth the eggs, salt and sugar. Fold in apples, nuts, flour, baking powder and vanilla. Pour batter into a greased, 10-inch baking dish and bake at 325 degrees for 1 hour. Cool. Serve with ice cream or sweetened whipped cream.