Cream together butter, cream cheese and Splenda until light and fluffy. Beat in the eggs one at a time. Stir in vanilla extract. Combine peanut flour, guar or xanthan gum, and baking powder. Beat the flour mixture slowly into the butter mixture. If desired, chopped nuts or sugar free chocolate chips can be added at this point.
Pour batter into prepared loaf pan. Bake for 50-60 minutes or until golden brown and toothpick inserted in center comes out clean. Allow to cool about 10 minute, then remove from pan and cool on rack.