Add ½ cup softened butter to a large bowl. Add in 1 Tbsp ground flaxseed, 1 Tbsp ½ cup white sugar, and ¼ cup brown sugar and cream together until evenly combined.
Add in one egg, 1 tsp vanilla, 2 Tbsp + 1 tsp water and mix together.
Add in dry ingredients: 1 cup flour, ⅛ cup brewers yeast (⅛ cup = 2 Tbsp), ½ tsp baking soda, ¼ tsp salt, ¼ tsp cream of tartar, and 1¼ cups old fashioned oats. Stir together until evenly combined.
Scoop out 2 Tbsp of dough and roll into a ball. Place 2 inches apart onto a baking sheet. Repeat with remaining dough.
Bake for 10-12 minutes at 350°F or until edges of the cookies are golden. Remove from the oven and allow to cool.