Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9 inch round cake pan.
In a small bowl, stir together 1 cup flour, baking powder and salt. Set aside.
In a large bowl, cream together 1/2 cup butter and 1/2 cup sugar until light and fluffy. Beat in the eggs one at a time, then stir in the vanilla. Gradually stir the dry ingredients into the creamed mixture. Finally, stir in the pecans and walnuts.
In a small bowl, mix together the oats, 1/4 cup sugar, 1/4 cup flour and melted butter. Sprinkle over the cake batter.
Bake for 30 to 35 minutes in the preheated oven, or until a knife inserted into the center of the cake comes out clean.
Remove from oven and cool in the pan for 10 minutes before inverting onto a wire rack to cool completely.
Interesting Facts
The pecan tree is native to North America and is a relative of the hickory tree.
Pecans are an excellent source of manganese, vitamin B1, magnesium and phosphorus.
Pecan coffee cake is the perfect treat for a special breakfast or brunch.