Ingredients

Browned Butter

1/2 cup unsalted butter

Topping

5 Tbs unsalted butter
1/2 cup firmly packed light brown sugar
1/4 tsp ground cinnamon
1/8 tsp ground nutmeg
3-4 Italian plums, pitted and thinly sliced

Cake Batter

1/2 cup firmly packed light brown sugar
1/4 cup white sugar
|3/4 tsp salt
1/2 tsp ground cinnamon
1/4 tsp ground nutmeg
1 1/2 cups superfine blanched almond flour
3 large eggs
1 Tbs freshly squeezed lemon juice
1 tsp almond extract, or to taste
1 tsp vanilla extract
6 Tbs all-purpose flour
3/4 tsp baking powder

Directions

1. Preheat oven to 350 degrees. Generously butter a 9-inch round cake pan and line the bottom with parchment paper.
2. Place 1/2 cup butter in a light-colored saucepan over medium-low heat. Cook, stirring constantly, until butter is browned, 5 to 7 minutes. Pour browned butter into a large mixing bowl; allow to cool for at least 10 minutes.
3. For topping, place 5 tablespoons butter in the same saucepan you browned the butter in; allow residual heat to melt it (or melt over very low heat). Pour melted butter into the prepared cake pan; sprinkle with brown sugar, cinnamon, and nutmeg. Gently mix ingredients together in the pan, then spread into an even layer. Arrange sliced plums over the butter-sugar mixture in a circular pattern, gently but firmly pressing the plums into the mixture, until the bottom of the pan is evenly covered. Set aside.
4. For cake: to the bowl with browned butter, add brown sugar, white sugar, salt, cinnamon, and nutmeg. Mix until combined. Stir in almond flour until incorporated (mixture will be grainy). Add in eggs 1 at a time, beating well after each addition with an electric mixer. After last egg has been added, beat mixture for 3 minutes on medium-high speed until light and fluffy. Beat in lemon juice, vanilla, and almond extracts. Reduce speed and stir in flour and baking powder until just combined. Pour batter over the plums; spread gently in an even layer.
5. Bake in the preheated oven until cake is evenly browned and the center of the cake springs back when lightly touched, 45-55 minutes.
6. Cool cake in the pan for 10 minutes. Invert onto a serving platter. Gently peel off parchment paper and allow cake to cool completely before serving.