Add all the ingredients for the crumb topping to a bowl, except the butter and mix together. Pour in the melted butter and mix until combined, then set aside.
Add the flour, baking powder, oat fiber and salt to a bowl and whisk together, then set aside.
Then add all the remaining ingredients, except the blueberries, to a large mixing bowl and mix using a hand mixer for about 30 seconds. Add in the dry ingredients and continue mixing.
Fold in the blueberries gently, then pour into a 9" x 5" nonstick loaf pan that's been sprayed with nonstick spray (I used coconut oil spray). If your pan isn't nonstick, I would line it with parchment paper. Smooth the top using your spatular and top with the reserved crumb topping.
Bake for 45-50 minutes or until a toothpick, when inserted, comes out clean.
The Oat Fiber is important in this recipe, as it gives a great bread-like texture. I use Lifesource Foods Oat Fiber 500, because it’s ground to a fine powder and has a very mild flavor.Oat Fiber is not the same as Oat Flour, which is made from grinding oats. Oat Fiber is made from grinding the outer husks of oats and is pure insoluble fiber. Insoluble fiber does not dissolve in water and is not broken down in the digestive tract, so it’s Low Carb and Keto friendly.