Beat eggs until light.
Add sugar, vanilla, rum flavoring, and butter; continue beating until well blended.
Sift flour and measure; sift with baking powder and salt into the first mixture.
Mix to a smooth batter.
Add the fruits and nuts.
Blend with a spoon or your hands until well mixed batter will barely coat fruit mixture.
Turn into a well greased 9-inch square pan; distribute batter evenly.
Bake in a moderately slow oven (325°) for 40 to 45 minutes.
Let cake stand in pan until partially cool; turn out on cake rack to cool thoroughly before storing.
Age the cake at least 4 days before cutting.
Cut in thin slices or in 1-inch squares.
It is easier to get perfect slices if you freeze the cake and cut it while hard.
The slices defrost in a very short time.