Place 1½ cups whole milk yogurt in a sieve or fine-mesh strainer lined with a paper towel over a bowl. Let sit for 30 minutes or up to overnight in the fridge.

Transfer yogurt to a bowl and stir in 2-3 tablespoons maple syrup and ¼ teaspoon vanilla extract. Refrigerate until ready to use.

Preheat the oven to 350 degrees F. Trace one 5-inch cake pans onto parchment paper and cut out three rounds. Trim slightly to fit inside each pan.

Grease three 5-inch cake pans with nonstick spray and place a round of parchment inside each. Grease again.

In a medium bowl, whisk together the oat flour, baking powder, and salt.

In a separate medium bowl, whisk together the melted butter, maple syrup, eggs, and vanilla until smooth.

Add the flour mixture to the wet ingredients and stir until just combined. Divide the batter evenly between prepared cake pans, using about 1⅓ cups batter in each pan.

Bake until a toothpick inserted in the center comes out clean, about 22-26 minutes. Remove from oven and place pans onto a wire rack. Let cool for 10 minutes in the pans, then carefully invert to cool fully. Discard parchment paper rounds.

To assemble, place one cake on your serving plate. Top with about ⅓-½ cup of frosting, spreading in an even layer just past the edges.

Add the second cake, repeat with frosting, and then repeat with the third cake.

Use an offset spatula or knife to scrape off the frosting overhang for a 'naked' cake look, or use additional frosting to coat the entire cake. Top with berries and serve.