Preheat oven to 325ºF.
Mix the flaxseed meal with 6 Tbsp. water and set aside to let thicken (5-7 minutes).
Mix together the nondairy milk and the vinegar, mix well, and set aside to let curdle (this makes a homemade vegan buttermilk!).
Sift together the dry ingredients (flour, cocoa powder, baking powder, and salt). Add the sugar and mix well.
Pour in the wet ingredients (flax eggs, vanilla extract, melted butter, and buttermilk). Mix well until smooth.
Pour into the greased wells of a donut pan. Bake 15-17 minutes. Remove from oven and let cool fully.