In a large bowl, mix together the butter, sweeteners, salt and cinnamon until creamy and fluffy.
Mix in the eggs until well combined then stir in the vanilla and Greek yogurt.
In a separate bowl, mix together the bb, oat fiber, baking powder, and cream of tartar.
Add to the cream mixture and mix until well combined.
Place the batter into a loaf pan or 4 mini loaf pans or muffin tins.
In a bowl, mix together 3 tsp of super sweet and 1 tsp of cinnamon and sprinkle over the batter.
In a preheated oven to 350° bake for 65-70 minutes for loaf (cover loaf pan with foil after 30 minutes to prevent the top burning) 35-40 minutes for 4 mini-loaves, or 15-20 minutes for muffins. Test center of bread with cake tester. When tester comes out clean bread is read. Allow to cool and enjoy!
I suggest super sweet for the topping on this bread because it will stay more crystalized. If you were to use a powdered sweetener like gentle sweet it would just melt into the top.