Preheat oven to 350°F (175°C).

In a large bowl, combine oat flour, all-purpose flour, spelt flour, chia seeds, cinnamon, ginger, baking soda, and rolled oats.

In a separate bowl, whisk together yogurt, vanilla extract, maple syrup, and eggs until creamy and thick.

Stir chopped apples into the wet ingredients.

Gradually add the dry ingredients to the wet ingredients, mixing until just combined.

Do not overmix the batter.

Gently stir in raisins and chopped walnuts until evenly distributed.

Pour the batter into a buttered 9x11 inch cake pan.

The batter will be fairly thick.

Tap the pan a few times to spread the batter evenly.

Bake for 30 minutes, or until a toothpick inserted into the center comes out clean.

Let the cake cool completely in the pan before slicing and serving.