Preheat your oven to 350°F (175°C) and grease a 9-inch round cake pan with 3 tablespoons of unsalted butter.

Sprinkle 3 tablespoons of brown sugar evenly across the bottom of the pan and arrange hulled and thinly sliced strawberries tightly in a single layer on top.

In a medium mixing bowl, combine whole wheat flour, all-purpose flour, cinnamon, baking powder, baking soda, and kosher salt. Whisk until well blended.

In a stand mixer, cream together the remaining 8 tablespoons of butter and ½ cup of brown sugar on medium speed until light and fluffy, about 5 minutes.

Add in the egg and vanilla extract, mixing for another 2 minutes until fully combined.

Gradually add the dry ingredient mixture to the creamed butter and sugar, alternating with Greek yogurt, mixing until just combined.

Spoon the batter over the strawberries in the cake pan, smoothing the top for even baking.

Bake for 25 to 30 minutes until a toothpick inserted in the center comes out clean and the top is lightly golden.

Allow the cake to cool in the pan for 15 minutes before inverting it onto a serving platter and let it cool completely.