Strawberry-Rhubarb Upside-Down Cake with Yogurt

Preheat oven to 350°F.

Toss rhubarb, strawberries and lemon juice in a large bowl.

Heat 1/4 cup brown sugar and 2 tablespoons butter in a 10-inch ovenproof skillet, preferably cast-iron, over medium heat, stirring constantly, until the butter melts and the mixture starts to bubble, about 3 minutes. Let cool for 5 minutes. Coat the sides of the skillet with cooking spray. Using a slotted spoon, arrange the strawberry-rhubarb mixture in the pan (discard the juices left behind).

Whisk flour, baking powder, baking soda and salt in a medium bowl. In another medium bowl, beat the remaining 3/4 cup brown sugar, 2 tablespoons butter and oil with an electric mixer on medium-high speed until light and fluffy, about 1 minute. Beat in eggs, one at a time. Add yogurt and vanilla and beat until smooth. Add the flour mixture and mix on low speed just until it is incorporated. Spread the batter over the fruit.

Bake the cake until it pulls away from the sides and the top is golden brown, 30 to 40 minutes. Let cool in the pan on a wire rack for 10 minutes. Run a knife around the edges and carefully invert the cake onto a serving platter. Let cool for at least 15 minutes more before serving. Serve warm or at room temperature.