Preheat oven to 350 degrees F. Spray bundt pan with nonstick cooking spray and set aside.
Make flax egg by combining ground flaxseed with warm water. Stir and set aside for 5 minutes to gel up. Make the vegan buttermilk by combining the non-dairy milk with the apple cider vinegar. Whisk and set aside to curdle for 10 minutes.
In a large mixing bowl, whisk oil, sugar, and eggs together. Whisk in the milk mixture.
In a separate bowl, add flours, baking powder, salt, cinnamon, and nutmeg and whisk to fully combine. Then slowly add dry ingredients to the wet ingredients. With a wooden spoon, gently fold and stir until well combined. Make sure not to over mix it.
In a small bowl, combine the brown sugar, walnuts, cinnamon, and nutmeg.
Layer into the bundt pan as follows: 1/2 batter, 1/2 streusel, 1/2 batter, and top with the remaining streusel.
Bake for 50-60 minutes or until a toothpick inserted comes out clean. Allow to cool on a wire rack for 10 minutes. Turn over onto a plate and serve warm.
Enjoy!
Wrap leftovers in plastic wrap or store in a big ziploc bag so it can stay moist. When you want to eat it again, cut a slice, and warm it up in the microwave for 20 seconds.
(Adapted from The Sweet Tooth Life)