Preheat oven to 375 degrees F (190 degrees C). Lightly grease a large baking sheet.
In a large bowl, mix together flour, sugar, baking soda, baking powder, salt and margarine.
Stir in 1 cup of buttermilk and egg.
Turn dough out onto a lightly floured surface and knead slightly.
Form dough into a round and place on prepared baking sheet.
In a small bowl, combine melted butter with 1/4 cup buttermilk; brush loaf with this mixture. Use a sharp knife to cut an “X” into the top of the loaf.
Bake in preheated oven for 30-40 minutes, or until a toothpick inserted into the center of the loaf comes out clean. Continue to brush the loaf with the remaining butter mixture while it bakes.
Let rest for 10-15 minutes before slicing and serving.