Beat the eggs with the sugar and gradually add the mixed together oil and cream, then the flour mixed with baking powder and vanilla. Beat well to a smooth cake mixture.
Smear a form with the butter and pour in 1/2 the cake mixture, distribute the mixed walnuts and dried fruits, pour the remaining mixture on top.
Put the cake to bake in a moderately heated oven. Don't open the oven until it swells well. Finally, check to see if it's ready with a toothpick.
After it cools for 10-15 min., invert the baked cake onto a platter. Sprinkle with sifted powdered sugar if desired.