Preheat oven to 350 F, Line two baking sheets with parchment paper.
In a large bowl, mix together oats, flours, baking soda, spices, salt, and xanthan gum, set aside.
In a stand mixer - or with a hand mixer - cream butter and lard together until smooth. Add sugars, a little at a time, until fully combined and fluffy.
Add egg, banana, and vanilla to the sugar mixture, continue beating until well combined and smooth.
Pour sugar mixture and raisins - if using - into the dry ingredients, mix just until well combined.
Chill dough for 1 hour
Use an ice cream scoop or Tablespoon to portion out cookies onto prepared baking sheets, leaving 2-3" between each of them.
Using clean wet fingers or back of ice cream scoop, slightly flatten each cookie.
Bake for 15-18 minutes, or until golden brown.
Allow cookies to cool on baking sheets for at least 5 minutes before moving.