Flourless Rhubarb-Almond Upside-Down Cake

Preheat oven to 350°. Place butter in a 9-inch round cake pan. Place pan in oven for 5 minutes or until butter melts. Remove pan from oven. Sprinkle almonds over butter in pan. Arrange rhubarb over almonds in a single layer. Sprinkle with 1/2 cup of the sugar.

In a small bowl, stir together almond flour, baking powder and salt; set aside. In a large bowl, beat egg yolks, 1/4 cup of the sugar, the almond extract and vanilla with an electric mixer on high for 2 minutes or until light and thickened. Stir in flour mixture.

Thoroughly clean and dry beaters. In a medium bowl, beat egg whites until soft peaks form. Gradually add remaining 1/4 cup sugar, beating until stiff peaks form. Fold egg white mixture, one-fourth at a time, into egg yolk mixture. Spoon batter over fruit mixture in pan, spreading evenly.

Bake for 30 minutes or until top is golden brown and springs back when lightly touched. Cool in pan on wire rack for 10 minutes. Loosen cake from sides of pan. Invert onto a serving plate, replacing any rhubarb that stays in pan. Serve warm or cool.