In a large bowl or the bowl of a stand mixer fitted with the paddle attachment, cream the coconut oil (or butter), Greek yogurt, coconut sugar, and granulated sugar with an electric mixer on medium speed until very light and fluffy, about 4 full minutes, stopping to scrape the bowl as needed.
Add egg, lemon zest (if using), and vanilla. Beat until incorporated, scraping down the bowl as needed. The mixture will look curdled, but do not fret. Beat in the baking soda and salt until combined.
Reduce the mixer speed to low and gradually add the all purpose flour and white whole wheat flour, mixing just until it disappears. The dough will look crumbly.
By hand with a rubber spatula or wooden spoon, stir in the coconut. For the best flavor and to make sure the cookies are not too dry, refrigerate for at least 1 hour or overnight.
When ready to bake, place a rack in the center of your oven and preheat the oven to 350 degrees F. Line a baking sheet with parchment paper or a silicone baking mat. With a cookie scoop or spoon, portion the cookies by heaping tablespoons, spacing them 1 inch apart on the prepared baking sheet. Bake for 8 to 9 minutes, until barely dry on the top and edges but still soft inside. Let cool on the baking sheet for 5 minutes, then gently transfer to a cooling rack. (I like to slide my piece of parchment or silicone baking mat right off the baking sheet and onto the cooling rack.) Enjoy warm or at room temperature.
*The coconut oil needs to be in a solid room-temperature state (like this), not already liquified.
TO STORE: Store leftover cookies at room temperature in an airtight container for up to a week (as if they’ll last that long!).
TO FREEZE: Place baked cookies in an airtight, freezer-safe container for up to 3 months. Let thaw overnight in the refrigerator, then transfer to room temperature. Or portion and freeze the dough; bake from frozen, adding to baking time as needed.