Preheat the oven to 350°F (175°C). Prepare your cake pans by greasing them lightly and lining the bottoms with parchment paper for easy release.

Whisk together the all-purpose flour, baking soda, baking powder, and kosher salt in a medium bowl until well combined.

Beat the egg whites in a large bowl with an electric mixer until stiff peaks form.

Cream the unsalted butter and vanilla Greek yogurt together until smooth. Then, mix in the maple syrup and vanilla extract.

Alternate adding the dry ingredient mixture and oat milk into the butter mixture.

Fold in the whipped egg whites gently using a spatula.

Divide the batter evenly between the prepared pans and bake for 20-25 minutes.

Cool the cakes in the pans for about 10 minutes, then transfer to wire racks to cool completely.

Frost your cooled cakes with the healthy vanilla buttercream or the dairy-free chocolate frosting.