Strawberry Rhubarb Upside-Down Cake

Move the oven rack to the middle position and preheat to 350 degrees F (175 C). Toss the strawberries, rhubarb, 1/2 cup of sugar and potato starch together in a bowl.Arrange the strawberries along the bottom of a non-stick 9" round or 8-inch square pan so that the cut sides face down. Top with the rhubarb and any remaining liquid, using the rhubarb to fill in the gaps between the strawberries.

Whisk together the flour, baking soda, and salt. In the bowl of al electric mixer, whisk the butter and 3/4 cup sugar together until light and fluffy ( about 2 minutes).

Add the eggs one at time and continue whisking until fully incorporated.

Add the yogurt and vanilla extract and whisk to combine. Switch to the beater attachment and add the flour mixture in three additions beating on low speed until just combined after each addition.

Spread the batter over the fruit and put the pan in the oven.

Bake until a toothpick inserted into the middle of the cake comes out without any batter on it (30-40 minutes).

Let the cake cool for 20 minutes. Run a knife along the edges if need be and then invert onto a large plate. If some of the fruit remains stuck to the pan, just stick them back into the cake.