Heat oven to 350°F. Sift together cake flour and nutmeg into medium-size bowl.
In separate large bowl, beat egg whites and cream of tartar until frothy. Beat in superfine sugar, 2 tablespoons at a time, until stiff, but glossy peaks form, 5 to 7 minutes.
Fold flour mixture into egg whites in 2 additions, until incorporated. Transfer half the batter to clean bowl. Fold cocoa power into half the batter in one bowl.
Alternately spoon white batter, then chocolate batter into ungreased 10-inch tube pan. Swirl with sharp knife to create marbled texture.
Bake in 350°F oven for 40 minutes. Remove from oven and immediately invert onto baking sheet or neck of bottle. Cool completely.
Meanwhile, combine the strawberries, granulated sugar and orange juice in a bowl. Let stand for flavor to mellow.
To serve, slice cake, and top slices with strawberry mixture.