Preheat the oven to 350. Spray or grease the bundt pan well and set aside. Whisk flax and water together and set aside to gel.
In a large bowl whisk dry ingredients.
In a separate bowl whisk sugar, kefir, oil, orange juice and vanilla together well. Add in eggs (or flax eggs) and whisk to combine. Add wet to dry folding in mixture until no flour remains. Batter may appear quite thick. Thats ok!! Add in zest and blueberries and gently mix. Transfer batter to prepared bundt pan, smoothing it out with an offset spatula. Place in the oven on the middle rack for 45 minutes. Check for doneness with a toothpick. Leave bundt cake in the pan for 10 minutes and then turn out onto the cooling rack. Cool completely before glazing.
To make the glaze simply add sugar and juice together and whisk to combine. Pour over cooled cake and enjoy!
*Macros are provided as an estimate for convenience. Your final numbers will vary depending on ingredient brands, substitutions, and how you portion the recipe.