1. Heat oil in a deep-fat fryer or deep heavy skillet.
Time heating so it will be ready when you are prepared to begin frying doughnuts. Use Canola oil if you prefer, but peanut oil has a higher smoking point and is a good choice for frying.
2. In a large bowl, combine flour, sugar, baking powder, salt, cinnamon, and nutmeg. Cut in margarine using a pastry blender or two knives.
3. Make a well in center of mix and add mashed bananas and eggs. Mix well. You can do this with a wooden spoon, or since dough will be very stiff you may want to use your hands to mix it well.
4. Place dough on a lightly floured surface and roll to 1 cm thick. Cut with a 2- half inch doughnut cutter that you dip in flour as needed.
5. Deep-fry, a few at a time, until golden brown. Drain on brown paper bags. Fry the doughnut "holes" also.
6. Combine sugar and cinnamon in a paper bag or place on a shallow plate. Coat warm doughnuts with this mixture.