Delicious variations on a well-known cake

There are a number of reasons that sponge cake is a sensible, simple, yet elegant dessert choice. Not only can it be varied by using different flavorings such as vanilla, grated orange or lemon peel, cocoa, chocolate chips, or almonds, it can also assume many shapes.

It can be a jelly or sponge roll, Baked Alaska, fruit flan, torte, sponge layer, Boston cream pie, tube cake, cupcakes, or petits fours. And leftover sponge cake is the start of the classic English Trifle.

It is sometimes called ''foam cake,'' because it depends for its leavening on the expansion of the vapor trapped in its egg-rich dough. Even when baked a day or two before serving, it will not lose its moisture.

Unfrosted sponge cake freezes well and will keep up to two months when wrapped airtight in freezer paper. To thaw, let stand in wrapping at room temperature for two hours. Before serving frost, fill, or both, or sprinkle with confectioners' sugar. Basic Sponge Cake 1 1/4 cups flour 1/4 cup cornstarch 1 1/2 cups sugar, divided 1 teaspoon salt 8 eggs, at room temperature 1 teaspoon cream of tartar 1/4 cup cold water 1 teaspoon vanilla 1 tablespoon lemon juice 1/2 teaspoon grated lemon rind

Sift flour, cornstarch, 3/4 cup of sugar, and salt onto square of wax paper. Set aside.

Separate eggs, dropping whites into deep bowl and yolks into large bowl. Beat whites with cream of tartar until thick but still soft. Add remaining sugar very gradually, beating vigorously until stiff and glossy.

Beat yolks with water, vanilla, and lemon juice until golden, very thick, and creamy - at least 5 minutes. Add dry ingredients to yolks gradually.

Beat at medium speed until smooth and thick. Fold in 1/4 of egg whites to lighten, then fold in remaining whites and lemon rind.

With wax paper, line bottoms of 2 ungreased 8-inch round layer pans or 2 rectangular 13 1/4-by-9 1/4-by-5/8-inch pans or one 9-inch tube pan.

Bake in 350-degree F. oven 18 to 20 minutes for layers, 10 to 12 minutes for rectangular sheets, 30 to 40 minutes for tube pan, or until cake springs back when lightly touched on top and is lightly browned.

Invert cakes on wire rack and cool completely before handling. Remove from pans and pull off wax paper.

Use your imagination in filling round layers. Possibilities include cream or lemon custard; sliced fruit, coconut and whipped cream; strawberries or other berries and cream; or preserves.

Here is an example of how sponge layers can be used for a fruit flan: Sponge Fruit Flan

Basic sponge cake, cooked in 2 8-inch round layers

1 cup raspberry, strawberry, apricot, or peach jam, or cherry or apple jelly

2 tablespoons orange juice or water

1 1/2 cup raspberries, whole strawberries, apricot halves, sliced peaches, pitted cherries, or poached apple slices

Freeze one layer of sponge cake for future use or double the fruits and glaze to make two flans.

Melt jam or jelly. Select one that best complements the fruit you are using in the flan. Add orange juice and mix. Brush a small amount of glaze over cooled layer.

Cover top with rows of raspberries, strawberries, cherries, peaches, apricot halves, fresh whole strawberries (pointed ends up), or poached apple slices.

Brush fruit with remaining glaze. Serve within a few hours. Top with whipped cream, if desired. Serves 6 to 8.