01 - Preheat the oven to 350°F (175°C). Line an 8x8-inch (20x20 cm) baking pan with parchment paper or lightly grease it.
02 - In a large bowl, whisk together oats, flour, brown sugar, baking powder, baking soda, salt, ground ginger, and cinnamon.
03 - In a separate bowl, whisk the eggs, melted butter, Greek yogurt, applesauce, and vanilla extract until smooth.
04 - Pour the wet ingredients into the bowl with the dry ingredients and mix until just incorporated. Avoid overmixing.
05 - Gently fold in the sour cherries, crystallized ginger, and any optional nuts.
06 - Spread the mixture evenly into the prepared baking pan. Bake for 32-36 minutes, or until the edges are golden brown and a toothpick inserted into the center comes out clean.
07 - Allow the squares to cool completely in the pan on a wire rack before cutting into 12 portions.